There's been some speculation about Diablo 3 launching on November 15, 2011. The reason for this is because Chris Metzen had said "The Book of Cain" would be released simultaneously to the launch of D3. And, Amazon.com accidentally posted a release date of Nov 15 for the book. Sources? [LINK 1] [LINK 2]

But while you're speculating, please remember the following releases;

Nov 01 Uncharted 3
Nov 08 COD: MF3
Nov 11 Minecraft
Nov 11 "Scrolls" Skyrim
Nov 15 Saints Row The Third
Nov 15 Assassin's Creed: Revelations

There's a LOT of competition around the 11/11/11 date, and Blizzard wouldn't risk releasing their game around such other high profile games. I think it would be safe to assume that Blizzard won't be releasing any games around the 12/12/12 period either.