Honestly the game looks pretty ready, its even been said that the final touches are being made during Dan Housers Q&A. He said "at this point were adding, removing, replacing and fixing bugs etc."
With that said, I'd go for a mid to late march release as the game is practically finished and its going through to final polishing stage before going gold and ready to be packed in boxes for transport to stores worldwide. 3 months is plenty of time for it to be completely finished, especially with the huge amount of artists and programmers said to be working on it.
But there is also a possibility for a delay, which is most likely why rockstar has given us a seasonal date rather than a day.