Rockstar has more or less confirmed that there will be no new details regarding GTA V until after Max Payne 3 is released in May. Here is what they said:
First of all, we'd like to again thank you and everyone out there for the amazing response to the debut Grand Theft Auto V trailer. We know that there are a ton of questions you all have about the game, including release date and lots else.
Right now, we are very hard at work on the game and are excited as well to show and tell you more as development progresses - expect that we'll be talking much more about GTAV starting at some point in a few months' time.
Please hang tight until then and thank you all for your patience and support!