Wrathion is back again in Patch 5.4, first asking you to meet him at the Tavern. He has learned of the new Timeless Isle, and wants to further augment your cloak by "time-locking" it. You will have to head to Timeless Isle and collect 50 Timeless Coin for one step in the quest. While you are doing that, you also have to defeat the four August Celestials of Pandaria in combat. Once you have completed both steps, you head to the Seat of Knowledge so that Wrathion can augment your cloak once more.
After having your cloak upgraded, there is one final quest to kill Garrosh. Wrathion reveals to you that this was his plan all along.
Redesigned Arena System - one of the first things you'll notice is that you'll no longer need to join or create an Arena team to compete. Instead, queuing will work much as it does for Rated Battlegrounds: you can queue for an Arena battle in a party of the appropriate size (2v2, 3v3, and 5v5), and your opponents will be selected based on the average Match Making Rating of your party.
For the most part, the mechanics of Arena will remain the same. You'll still gain and lose personal rating based on your wins and losses, though your Conquest Point cap will now be based on your Personal Rating. The rating requirements to purchase items will also be based on your Personal Rating.

Patch 5.4 was deployed on the PTR, the patch includes new raid and new raid difficulty.
New Features
Siege of Orgrimmar - new raid.
Timeless Isle - new zone.
Flexible Raid Difficulty - this is a new raid difficulty designed for pre-made groups of 10 to 25 players or any number in between. This means it's possible to have raids of 15 or 22 players! Difficulty will adjust automatically based on the number of players present with encounters intended to provide a challenge roughly between Raid Finder and Normal difficulty.
Loot quality will be between Raid Finder and Normal difficulty and awarded through a personal loot system (similar to Raid Finder). Bonus rolls and loot specialization will also be supported.
Players will be able to earn raid achievements just like in Normal or Heroic difficulty.
Flexible Raid difficulty has a lockout that is separate from Raid Finder and Normal difficulty.
Proving Grounds - is a new feature for individual players to test and improve their combat skills.
At the Proving Grounds, players may undertake trials, designed for Damage, Tank, or Healer roles.
It provides a great opportunity to learn how to Tank or Heal, without the need of a group.
Each trial is available in four separate difficulties: Bronze, Silver, Gold, and Endless. Harder difficulties include more difficult and varied enemies.
Endless mode allows you to test your mettle against increasingly difficult enemies. Compare your best scores to friends and guildmates!
Virtual Realms - are sets of realms that are fused together, and will behave exactly as if they were one cohesive realm. Players on the same Virtual Realm will be able to join guilds, access a single Auction House, join arena teams and raids, as well run dungeons or group up to complete quests. Players belonging to the same Virtual Realm will have a (#) symbol next to their name.

The new Battle.net desktop client has been tested internally for some time now. It appears that testing is nearly here, as the Battle.net support site has been updated with related help articles.
Currently only a Windows version has appeared for testing, but by the looks of the jobs page, a OS X version is in development as well.
This replaces the launcher for all Blizzard games, and works similar to the current launchers, with background updates, repair tool, and more.
Chat with Battle.net friends across every Battle.net enabled game.
News - you can see all of the news from the various Battle.net game sites in the client.
Store, Forums, Profiles - not yet implemented.
Patch 5.3 Features
Darkmoon Faire - the Faire is now a Cross-Realm Zone.
Death Knight - one per Realm restriction removed.

Patch 5.3 - Escalation is going live this week, less than three months after Patch 5.2 went live.
New Features
Heroic Scenarios give 120-150 Valor Points for your first every day, and a chance to get an item level 516.
Challenge mode daily quest also gives you a chance at item level 516 gear.
The legendary quest line continues, with a reward of item level 600 cloaks.
The Kor'kron have taken over the Troll area in Orgrimmar, as well as Razor Hill, and are advancing on Sen'jin Village. You will team up with Thrall, Vol'jin, and Chen Stormstout to push them back and retake Razor Hill.
The weekly Barrens quest will give you a chance to buy an item level 489 item.
There are several new mounts in this patch, with the most interesting being the Enchanted Fey Dragon.
You can now use items in your bank and Void Storage for transmogrification.
A quest was added that will reveal the final Sha and reward you with item level 502 boots.
Four new scenarios, one battleground, and a new arena were added to the game.
The Brawler's Guild has some new bosses and other updates, along with some new shirts.
Heirloom shields are finally on the vendors.
You can now level mining and herbalism in Pandaria, no matter what skill level you are at.

New updates had been made on the PTR recently, including new Battleground and Heroic Scenarios.
New Features
Deepwind Gorge Battleground - this battleground is placed in the western part of the Valley of the Four Winds, in a gorge that is only present in the battleground, not in the regular world. This is a 15 player battleground for level 90 players.
The battleground has two different objectives, the first being the three mines. There is a northern Pandaren mine, central mine, and a southern Goblin mine. The mines are captured like the bases in other battlegrounds, just clicking the flag and capturing it. While you hold the mine NPCs will mine gold for your faction, bringing you closer to the 1600 resources required to win.
The second objective is the cart of gold placed at each faction's base. You can click the cart to attach it to yourself, and then walk back to your base to capture it. You do not need your own team's cart to be present to capture, unlike the normal battleground flags. Holding the cart limits your movement speed to normal running speed, with only things like Blink allowing you to get there faster. If you kill the enemy cart holder, you must click on the cart to return it to your base before someone on the other team clicks to pick it up.
Capturing the cart rewards you with 20 bonus honor, 200 resources, and the message that your faction has stolen gold from the other.
Darkspear Rebellion Quartermaster - Ravika sells several useful and novelty items. The epic Latent Kor'kron pieces cost 200 of the Barrens resources, 100 of one type and 100 of another. These are also dropped by the Kor'kron NPCs you are killing in the Barrens for the Battlefield: Barrens weekly quest, with roughly a 1% drop rate. They can be combined with a Radical Mojo from the weekly quest to create a piece of item level 476 spec appropriate armor.
The Raptorhide Boxing Gloves cost one Radical Mojo and grant access to a new Brawler's Guild boss. Gahz'rooki's Summoning Stone also costs one Radical Mojo.
Heroic Scenarios - your first Heroic Scenario of the day offers 120 Valor Points for completion and just 30 Valor Points for completing the bonus objectives. You will also earn a Heroic Cache of Treasures, which has a chance to drop epic item level 516.
Doing another scenario after the first reverts to the old Greater Cache of Treasures and 70 Valor Points plus 30 Valor Points for the bonus.

Congratulations to Method for defeating Ra-den 25 man in just two attempts this week!
New Features
In-game Browser and Support Tools - the browser is limited to the Battle.net support site only.
Battleground Roles - roles to queuing for random battlegrounds.
Loot Specialization Menu - allowing you to choose what spec you want loot for when getting bonus rolls, Raid Finder gear, and Pandarian quest rewards.
Transmogrify from Bank and Void Storage - now it's possible to transmogrify to items that are located in your bank or Void Storage without having them in your bags.
World Changes
The patch starts setting up the story for Patch 5.4 and brings the fight back to Azeroth. One of the first things Horde players will notice is the Troll area of the Valley of Spirits in Orgrimmar has been taken over by the Kor'kron Guard, with Kor'kron Overseers taking aim at the residents. The trainers, bank, auction house, and every other NPC has been shut down, only talking about how dangerous it is now.
Things aren't much better for the Trolls outside of Orgrimmar, as they are being kept in cages or down on their knees, blindfolded, in front of armed and Neutral flagged Kor'kron Grunts.
Further south in Razor Hill the Kor'korn have also posted guards, but operations are still continuing normally there. High Overseer Bloodmane has moved down to Razor Hill from his position outside of Orgrimmar.
Moving further south to Sen'jin Village, the guard presence there has been greatly increased, with the guards asking if you are going to help and saying "Welcome to da' revolution".