http://www.joystiq.com/2009/10/28/gt...isodes-manual/
Teaser from the back of the Episodes From Liberty City manual, although it is more than likely just to rile up the fans. It also says 'opening March' which is the date for Rockstar's Red Dead Revolution.
Either way, it's easy to believe the next GTA is out so early I suppose. They don't need to build a new engine or anything this time around as all of this is within the 'GTA IV' universe so to speak. It wont be called GTA V either, it will be GTA : Something.