Word has come down that RDJ signed a deal with Disney/Marvel to return for Avengers 2 and 3. No word on Iron Man 4 at this time.
Downey was reportedly asking for 100 Million to reprise the character. Large portions of this were to be paid to his fellow Avengers co-stars to supplement their meager (in comparison) salaries. No word on how that breaks down, nor will it likely be made public. Good job Iron Man!
The Skinny from the Fatty 