Ubisoft hasn't announced anything official for the release date for Splinter Cell: Blacklist, but that doesn't mean there isn't an official release date yet. Or, at the very least, it doesn't mean that retailers won't try to make an educated guess. Amazon usually guesses by the end of whatever year just to be safe, but occasionally they'll take a stab at a more specific date than December 31, 20XX.
Amazon UK currently says that Blacklist will launch on March 29th, which is a Friday and the typical release date for European games. As such, it is possible that this is not a stab in the dark, but a leaked release date for the game.
On the other hand, the Amazon listing for the US says Blacklist launches on April 1st, which is both a Monday—not the usual day of the week for game releases—and April Fool's Day. My first instinct is to call shenanigans on this one.
My second instinct is to be instantly relieved that it's not February, the second November.