“I don’t know how far out it is, but it’s still fairly early in development. I think when people see it, it feels so polished and so finished, but the reality is we have a very small portion of the game done right now. […] We have a long ways to go to build each of the different acts in the game and put in all the quests and all the different monsters. We have a lot of development ahead of us before it will be something … It will definitely be out after StarCraft II.”
Last Starcraft II rumor had the game scheduled for release “sometime in 2009”, so don’t make any plans for Diablo III. Furthermore, Starraft II is now known to be developed as a trilogy, so do expect different release date for each of the three campaigns.
To sum it up: you want DiabloIII? Then get ready to spend a lot of time in Purgatory!