I liked the nice "Heat" reference in the Michael GTA V trailer. I'm looking forward to playing as him in the main game. I have a feeling his son will probably die in the main story, unless he is going to be a weird comic relief sort of character within his story arc.
I see him in the Roman role from IV. I don't think we will get choices that will effect the ending of the game like we had in IV but I see him in that sort of role.