As shown in a NeoGaf message board, Ubisoft posted a flash file and a logo of the game on its official Facebook page.
The Facebook page has since been deleted but the image and flash file are traces of evidence that the game is indeed coming.
There’s no word when Assassin’s Creed: Revelations will be coming on Facebook but it won’t be any time soon. Judging by the fact that Ubisoft didn’t want its announcement to be so soon yet.