Grand Theft Auto V will be out on January 15, 2012. Or, well, at least if we're to trust this listing on the German Gamestop's website.
If it's true, then we can probably expect to see the game at E3 - there's been quite a lot of rumours that we would already, so it's far from impossible. It could also be that the German Gamestop is hoping for some people to put in pre-orders even before the game is announced, putting a random date on it, but that would of course be terribly cynical of us to say.