Diablo III has been, very sadly, postponed until early 2012. Their original release deadline has been thrown out, most likely from problems experienced with the recently-opened closed beta. Mike Morhaime, CEO and cofounder of Blizzard Entertainment, said,
The beta will be extended, though, so those who are in it get to play that for longer. While it's sad that the release will be postponed, we should all know by now that if Blizzard is postponing their release, it will be worth it. It's very unlike Blizzard to release an un-polished game, and Diablo III should be no exception. You can read the press release here.