he PTR is up and running for World of Warcraft

Thunder King Cinematic: The cinematic starts when you begin the scenario "Tear Down This Wall!" in World of Warcraft. Tear Down This Wall! is a scenario in World of Warcraft: Mists of Pandaria. It takes place in an instanced version of the Isle of the Thunder King.

Patch 5.2.0 is an upcoming content patch that will focus on the return of the Thunder King.

The first World of Warcraft: Mists of Pandaria patch of 2013 is currently in development and this is your chance to see some of the things that are in the works. This patch will include a massive new raid dungeon, a multi-faceted new quest hub, Pet Battle improvements, new world bosses, significant class balance changes, brand new pets and mounts, assorted bug fixes, and more.

Note: The Patch 5.2 PTR is not yet available, but you can feast your eyes on the latest version of the PTR patch notes below. Please keep in mind that these changes are not final, and a great deal could change before the final patch 5.2 release.
Look for the 5.2 PTR to become available in early January!