No amazon just says december 31 for every game that doesn't have a release date. I though it would come out this spring but they don't have any videos or even a box art, so I don't think that'll happen. I think an summer/fall release date is more likely.
Just be patient, perfection takes time. So if 2k wants to work on Bioshock Infinite to insure that its perfect then I say lets let them. I don't want them rushing out a game without making sure that it is the best it can be. Beside we got plenty of games to keep us occupied until then. Resident Evil Raccoon City Chronicles , Mass Effect 3, MG rising Revengence, and Max Payne 3.