That means that while the game might still make it out this year the publisher doesn't want to take any chances and promise a 2011 release date for the game and then have the game be delayed into 2012. Activision did say that if a delay happens than there will likely be two Blizzard games out in 2012. It's not clear if the second Blizzard game would be a new World of Warcraft expansion pack or StarCraft II: Heart of the Swarm. During the Q&A Blizzard CEO Mike Morhaime stated only that development of the game was going well and that more info on the title, including when the Diablo III beta will begin, will be announced in the future.
Gallery: Diablo III Screenshots