Blizzard on their unstoppable path of MMORPG success have teased the world with news that they are in the early stages of development of their fifth expansion for their super-successful World of Warcraft, which will be the successor to the as-yet-released Mists of Pandaria, and this is all from Blizzard's COO, Paul Sams.
Right now, the stage that the fifth expansion in is just the development of ideas and lore that end up shaping the landscape, classes and various other puzzle pieces that go into game development. Blizzard are so far into this, that they are already teasing ideas of a sixth expansion for World of Warcraft.
Blizzard had previously admitted that fellow MMORPG, Star Wars: The Old Republic, had bitten a bunch of their subscriber numbers away, but they are hoping that their panda-based expansion will claw those members back. The teasing of future titles works two ways: keeping players interested, excited and wanting the new titles as soon as they hit, and providing confidence that WoW is not losing its grip on the MMORPG market.