Check out the most popular specs for Mythic+ during the fourth week of Season 4.

.increase { color: #32CD32; } .decrease { color: #FF0000; } DISCLAIMER
The following post is based on data taken from u.gg, which has combined thousands of parses from live servers.
The Most Popular Specializations for Mythic+ in Season 4 Week 4
This week's affixes are Volcanic, Tyrannical, and Sanguine.
An upward arrow (▲) represents an increase in popularity, while a downward arrow (▼) represents a decrease, compared to the previous week.
The Most Popular DPS Specializations
Shadow Priest - 18.3% (▲0.4%) Retribution Paladin - 13.7% (▼0.2%) Augmentation Evoker - 12.3% (▲1.3%) Destruction Warlock - 6.1% (▼0.3%) Fire Mage - 5.8% (▲0.2%) Frost Mage - 4.5% (▼0.4%) Beast Mastery Hunter - 3.6% (▼0.1%) Outlaw Rogue - 2.6% (▼0.3%) Devastation Evoker - 2.6% (▼0.1%) Demonology Warlock - 2.4% (▼0.2%) Havoc Demon Hunter - 2.4% (no change) Balance Druid - 2.4% (▼0.1%) Arms Warrior - 2.2% (▼0.2%) Elemental Shaman - 2.1% (▲0.1%) Windwalker Monk - 2.1% (no change) Fury Warrior - 1.8% (no change) Unholy Death Knight - 1.6% (▼0.1%) Enhancement Shaman - 1.5% (▼0.1%) Arcane Mage - 1.5% (no change) Assassination Rogue - 1.5% (no change) Frost Death Knight - 1.5% (no change) Feral Druid - 1.5% (no change) Marksmanship Hunter - 1.5% (no change) Subtlety Rogue - 1.5% (no change) Survival Hunter - 1.4% (no change) Affliction Warlock - 1.4% (no change)
The Most Popular Tanks
Vengeance Demon Hunter - 64.1% (▼0.6%) Protection Paladin - 9.7% (▲0.2%) Guardian Druid - 7.7% (▲0.4%) Blood Death Knight - 7.6% (▼0.2%) Protection Warrior - 5.9% (▲0.4%) Brewmaster Monk - 5.0% (▼0.1%)
The Most Popular Healers
Restoration Druid - 37.0% (▲1.0%) Mistweaver Monk - 15.2% (▼1.0%) Holy Priest - 14.1% (▼0.1%) Restoration Shaman - 13.2% (▲0.6%) Discipline Priest - 7.1% (▲0.2%) Preservation Evoker - 7.0% (▼0.3%) Holy Paladin - 6.4% (▼0.4%)

Blizzard has further updated the Skyriding Talent tree in the latest War Within Alpha build. Find out what's new!
Here is a preview of the tree from last week's War Within Alpha Build. You've had all the Skyriding abilities listed at the top and were given just enough "Dragon Power" to unlock all the talents with two "free" choice nodes located on the right side.

Skyriding Talent Tuning in War Within Alpha Build 54774
Some Skyriding talents have been updated in the latest build:

Ground Skimming- When skyriding near the ground, you regenerate 1 Vigor every 30 15 sec. This effect does not occur while affected by Thrill of the Skies unless Swift Skimming is learned. Bronze Timelock- Mark a waypoint on your positional timeline. Use Bronze Rewind to rewind to this location. Can only be used in the Dragon Isles. Whirling Surge- Spiral forward a great distance, increasing speed. Whirling Surge evades Wingshredders and dismounts airborne enemy players Skyriding Basics- While falling from a high location, your mount extends its wings to propel you both forward. Pointing yourself downward grants more momentum. Evening out can transfer that momentum forward. Pointing yourself upward slows you down. When at your slowest, you will start to fall slowly toward the ground. You also gain access to the following abilities: Surge Forward Flap forward. Surge Forward evades Scalechillers, Scalechargers, and other obstacles encountered in time trials and races. Skyward Ascent Flap upward. Aerial Halt- Flap back, reducing forward movement. After activating Aerial Halt, experience a brief moment of weightlessness as the effects of gravity are reduced for 4 sec. Skyriding Proficiency
In the most recent TWW Alpha build, the Skyriding tree has changed a bit. Dragon Power [PH] has been renamed to Skyriding Proficiency and the tree layout has been simplified. It now has 6 tiers.
You will gain Skyriding Proficiency as you level up, but we currently cannot create low level characters on the PTR, only pre-made Level 70 template characters, so we cannot tell at which level you will gain Skyriding Proficiency.

Skyriding Talents in War Within
The tree now has 6 tiers of power (down from 9)
Tier 1
Take to the Skies - Your Vigor is increased to 4. Tier 2
Dynamic Stretching - Your Vigor regeneration rate is accelerated to 1 vigor every 25 sec while grounded. Second Wind - Reach within for untapped reserves and instantly generate 1 Vigor. Max 3 charges. Instant, 3 min recharge. Thrill Chaser - Thrill of the Skies generates 1 Vigor every 10 sec. Tier 3
Restorative Travels - Your Vigor regenration rate is accelerated to 1 Vigor every 0 sec while grounded. Tier 4
Aerial Halt - Flap back, reducing forward movement. after activating Aerial Halt, experience a brief moment of weightlessness as the effects of gravity are reduced for 4 sec. Instant, 10 sec cooldown Ground Skimming - When skyriding near the ground, you regenerate 1 Vigor every 15 sec. Tier 5
Dragonriding Learner - Your Vigor is increased to 5. Tier 6
Beyond Infinity - Your Vigor is increased to 6. Yearning for the Sky - Your Vigor reeneration rate is accelerated to 1 Vigor every 15 sec while grounded. At Home Aloft - Thrill of the Skies generates 1 Vigor every 5 sec. On the ride side, you have choice nodes that are free and do not cost Skyriding Proficiency.
The first choice node lets you enable/disable Riding Along. The second choice nodes lets you pick between Whirling Surge and Lightning Rush.

Reddit user Maleficent-Till6391 maxed out their cloak's stamina in MoP Remix and discovered it can't exceed 200K.
The Cloak of Infinite Potential isn't as limitless as advertised. One player managed to collect 200,000 Stamina and used theInfinite Thread of Stamina, but it didn’t increase their Stamina further. The cloak should theoretically be limited only by the 64-bit signed integer limit, which is 9,223,372,036,854,775,807.

For those interested, here are the player's cloak stats:

200,000 Stamina translates to 13,704,440 health. With the Bone Shield and MoP Remix consumable, it increases to 15,667,882, according to the OP.
Here are the player's stats with and without the cloak.

With a minor 10.2.7 fix we move right into the Remix stuff, as there's improvements to rare elite respawn and treasure, quests, dungeons and the open world. We also have Cataclysm Classic fixes, as honor vendors return, the high level PvP gear gets downgraded, quests get improved and more.
May 22 (Source)
Non-Player Characters
Doc Nanners in Valdrakken will again offer players "A Cataloger's Paradise" upon reaching Renown 8 with the Dragonscale Expedition. WoW Remix: Mists of Pandaria
Added clarity to the quest "The Great Water Hunt" to speak with Mudmug before gathering water. Nostwin now sells Glyph of Shadow for Priests. Fixed an issue preventing the quest "Where are My Reinforcements?" from proceeding as expected. Improved the respawn rate and treasure from rares and rare elites across Pandaria. Increased the amount of bronze and raised the drop chance for threads of time from airborne bronze. Fixed an issue where players who faction-changed could not use the group finder for dungeons and scenarios. Fixed an issue preventing the quest “Riding the Skies” from granting the appropriate Cloud Serpent mount. Fixed an issue causing Wise Mari in the Temple of the Jade Serpent to not spawn Corrupt Living Water as intended. Hutia was out of control in the Jade Forest, and has been convinced to relax a bit and stop hitting so hard. Cataclysm Classic
Fixed a bug preventing Diabolical Plans from dropping in Ashenvale for Horde players wanting to do “Never Again”. Cataclysm Honor Vendors should now be available in Stormwind and Orgrimmar to purchase ilvl 352 Blue PvP Gear for Honor Points. Conquest and Elite Conquest vendors will not sell anything until Arena Season 9 begins with next week's regional resets. Fixed a bug with the Thirty Tabards Fixed a bug preventing Engineers and Alchemists from making discoveries while crafting. Crafted “Vicious” gear that was unintentionally created at item level 377 has been adjusted to item level 339. In "Stonefather's Boon", the Stonefather's Boon buff duration has been reduced to 10 seconds (was 3 minutes). Fixed some quest issues. Erunak Stonespeaker should now still be visible to players who have advanced further in the quest line at the original location to turn in “Call of Duty”. “All or Nothing”, “Blood and Thunder”, and “Defending the Rift” should no longer fail to complete if you are sitting or mounted.

We have a lot more changes coming in to Remix today, starting with cloak thread rewards being added to most repeatable activities! Then there's the announced tuning for enemy damage and HP, gems and more, as well as some additional class adjustments over in Cataclysm Classic
May 21 (Source)
WoW Remix: Mists of Pandaria
We have made the following changes to improve Thread of Time gain for the Cloak of Infinite Potential. Our goal with these additional items is to give players access to more Threads of Time from daily repeatable sources. These should serve as readily attainable power-ups from a wide variety of content, so players can enjoy the breadth of Pandaria while also gaining additional power. There are four new items that grant players escalating amounts of power for the Cloak of Infinite Potential: Minor Spool of Eternal Thread Lesser Spool of Eternal Thread Spool of Eternal Thread Greater Spool of Eternal Thread Players will be able to find these new items from a variety of solo and group sources, ensuring all players have accessible ways to improve their cloak: Infinite Bazaar Repeatable Dailies First-Time Daily Scenario, Dungeon, and each LFR queue World Bosses Remix Achievements Each of these achievements are available for additional characters to complete as well for bonus Bronze - and now bonus Spools of Eternal Thread. Troves of the Thunder King scenario on the Isle of Thunder We’ve made the following changes and bugfixes are intended to address concerns about the balance of low- and high-level players in various Remix content. The health of creatures in heroic scenarios has been decreased by 20% - 25%, based on the players’ levels. Higher level players will see enemies incur a larger decrease. The health and damage of creatures on the Timeless Isle, Isle of Giants, and Isle of Thunder has been reduced. Several spell gems (that were not scaling up or down correctly based on player level) have been adjusted so that they provide a more-appropriate scaling effect. This includes Cold Front, Windweaver, Vampiric Aura, and Lightning Rod. Spell gems with shielding effects should no longer cause threat. Fixed a bug with Righteous Frenzy not canceling upon the end of combat. Timerunner’s Vial mana regen significantly increased. Adjusted the reputation granted from Granite Quilen to be more in line with expected values. Fixed an issue in Guo-Lai Halls causing trap tiles to flicker.  
Cataclysm Classic
Players experiencing phasing issues from Wrathgate or Battle for Undercity quests that are deprecated in Cataclysm Classic should now be in the correct phase in Orgrimmar and Undercity. Hunter Hunter traps are now faster and more consistent in their arming times. Shaman Fixed an issue with Shaman Greater Fire Elemental dealing too much damage with its Fire Nova spell. Warrior Fixed an issue preventing Slam from being logged properly in the combat log.