According to www.MMO-Champion.com Blizzard just filed for "Mists of Pandaria", and they are thinking it will be an expansion and not a book of some kind. As a former WoW addict, it is a bit upsetting with the trend of Blizzard churning out expansions at a faster rate, while charging or soon to be charging for "premium" content, like sending your BoAs to other realms. And with them showing off their Real Money AH in Diablo 3, it just feels like Blizzard is becoming more like Activision every single day.
http://www.mmo-champion.com/content/2399-Mists-of-Pandaria
http://www.mmo-champion.com/content/2399-Mists-of-Pandaria