According to several reports hitting the web this morning (this being one of them) Cliff "Cliffy B" Bleszinski of Epic Games confirmed that a sequel to the multi-million selling 360 shooter is indeed a given.
Following a few beers at the Game Developers Choice Awards ceremony in San Francisco, Cliffy B made a presentation early next morning, where he apparently confirmed the sequel would be happening. Gamespot has said that there are no further details on timing or plot available yet and we're still waiting for the old "official" word from either MS or Epic.
Maybe a new Gears announcement is part of Microsoft's surprise E3 attack?