I think that date is when Gamestop ships pre-orders, not the release date (they list the download version as available Jan 5th). Some places mail out pre-orders early, so they will arrive by the release date (they have to get games a little early anyway, to have time to re-distribute them to individual stores, etc). Some retailers put games on the shelves a little early, as well, though they are not suppose to (larger stores / chains may not want to risk annoying distributors / publishers).
