I think World of Starcraft is much more likely than World of Diablo, simply from a much larger fan base.
But then again, it is not likely at all. Next MMORPG from blizzard will be, obviously and completely undoubtedly without any question: World of Warcraft 2.
Edit: I would put any amount of money on it already being in production.
This post was edited by dysgenics on Aug 17 2010 08:40am