Episode II is speculated to be based around Luis Lopez (seen in missions like Three Leaf Clover; as one of the hostages, and in Museum Piece; he is the guy who turns up at the window when Johnny and Niko are handing over the diamonds.)
The speculation comes from the achivement gained from that very mission.
The impossible trinity
Who would be...Niko Bellic (GTA IV), Johnny Klebitz (Lost and the Damned) and Luis Lopez...
Episode II will be the last DLC from GTA IV