The Mists of Pandaria systems patch will be going live this week and it brings a lot of changes! Make sure your Background Downloader has downloaded the files so you aren't stuck waiting.
New Features
New Talent System - Now has 3 talents per tier, with 6 tiers.
Class Changes
New Ability Animations - So shiny
Experience Required to Level Changed - Reduced amount of XP to level to 85.
11th Character Slot - Unclear if it is coming in 5.0.4, but it will be for sure in Mists of Pandaria.
AoE Looting - Loot all of the corpses in an area around you with one click!
Scarlet Monastery and Scholomance Revamp - New lower level versions of the dungeons.
Dungeon and Raid Valor Reward Changes and Currency Conversion
Account Wide Achievements, Mounts, and Pets
Simplified Buff and Debuff System
Item and Stats Changes - Changes to expertise, Spell resistance, Resilience, and the stats on items.
New Druid Forms - Armored forms for Incarnation and a new Travel Form.
New Warlock Pets and Emotes
Cross-Realm Zones - Play with friends on other realms, no more empty world!
Interface Changes - New and easier to use interfaces, loot history, and more.

Mists of Pandaria opening cinematic made its debut at GameCon in Cologne.

Heroes of Azeroth, prepare to embark for an exotic new frontier! Mists of Pandaria is launching on September 25, 2012, and you can be ready to play when the servers go live by pre-purchasing the game digitally. Plus, for the first time ever, players will have the option to upgrade a pre-purchase to the all-new Digital Deluxe Edition, which comes with all of the in-game items from the retail Collector's Edition.
Beginning September 25, 2012, World of Warcraft players around the world will be able to set sail for the long-lost continent of Pandaria, where they'll explore forgotten dungeons, vanquish risen evils, and play their part in the Horde-Alliance conflict as it reaches a critical breaking point.
Whether you plan to level your existing character to 90 or start fresh with a new pandaren Monk, it's never too early to begin preparing for your adventure.

The largest games convention on Earth is happening in Cologne, Germany from August 15 to 19 this year. Blizzard Entertainment is excited to announce our presence at gamescom 2012, where visitors will have the chance to witness the world premiere of Mists of Pandaria opening cinematic. The latest creation from Blizzard's cinematics team will be shown on giant screens at our booth on Thursday, August 16, the first fully public day of the event.
We're also pleased to announce that this year we'll be showcasing Mists of Pandaria, Diablo III, and StarCraft II: Heart of the Swarm! Don't miss your chance to experience the games first-hand and to meet members of the development teams. In addition, be sure to get creative and join in our famous dance and costume competitions.
Visit the Blizzard Entertainment booth in Halle 6.1 (B21) at the Koelnmesse in Cologne and prepare to be epically entertained. For more information on gamescom, check out the official site.

During the past few beta builds, unknown items appeared on the Black Market Auction House (BMAH) that turned out to be epic quality ilvl 509 Heroic items. It also seems that some items are sold on the BMAH that are available from trainers currently, such as the [Pattern: Royal Satchel] for the new 24 slot bag.
The maximum bid has also increased to 999,999 gold.
The talent page at eu.battle.net has also been updated to the most recent beta build.

MMO-champion posted today the new login screen for Mists of Pandaria!