It's common sense to have your game play on the next-gen consoles from a business standpoint.
I'm sure Rockstar will announce it later.
Just think about it, with all the improvements and additions to their new game, do you really think that the current 7 year-old console will be able to play the game as they intended?
I can't wait to play it on my PS3, but it's probably a watered-down version, at least graphics wise.