RDJ's agent would be in a pretty strong negotiating position for Avengers 2, I think. I can easily see Marvel being somewhat generous but making it part of a three-movie package including Avengers 3 and Iron Man 4. After that, maybe they'll do a semi-reboot. Lowe might have made a good choice but that ship has sailed as he'd be in his fifties by then. Wouldn't bet against Colin Farrell.