World of Warcraft got its first expansion pack in 2007 with The Burning Crusade. Wrath of the Lich King followed the year after that, though Cataclysm, the latest expansion, didn't arrive until the tail end of 2010. Another one is virtually inevitable, and a new trademark filing by Blizzard Entertainment suggests that the title of the unannounced next expansion will be Mists of Pandaria.
The Mists title could be for any number of things at first glance, but MMO Champion notes that the international codes connected with the trademark registration -- 009 and 041, for computer game software and online entertainment services, respectively -- indicate that it's not a book title we're looking at. You can read about the Pandaria region of Azeroth right here.
Source: MMO Champion