While the release date was an open secret for several days, due to blue posts about the next arena season, now it is official: Cataclysm will be released on December 7th. Interestingly the press release suggests that the downloadable version from the Blizzard store will be available on the same date, although it doesn't explicitely say that.
By the way, anybody else here who thinks that a collector's edition for fully TWICE the price of the expansion is a bit overpriced?
[P.S. We all guessed wrong!]