Robert Downey Jr. is now in negotiations to join "Captain America 3" as fan favorite Iron Man.
Previous reports have been saying that Marvel has no plans to make a fourth "Iron Man" movie.
In statements, Downey will also be done with Iron Man in the second and third installments of Marvel's "The Avengers" Franchise.
Joe and Anthony Russo, the brothers who directed the popular and acclaimed Captain America: The Winter Soldier, are directing the third Captain America.
Marvel and Downey's agency, CAA, had no comment, but the talks, which are at a sensitive stage, could see the actor reap a $40 million-plus backend.
The actor made more than $50 million for his part in the first Avengers, and sources said he was looking for something similar.
But with a payday as large as this on the table, Downey will see what was initially envisioned as a brief role grow substantially, as some sources say the next storyline Marvel is seeking to adapt is the "Civil War" event series from 2006 to 2007.
That miniseries pitted Captain America against Iron Man in a storyline involving civil rights.
In the comics, the U.S. government passes a superhero registration act with the two heroes falling on opposite sides (Captain America is opposed to it, has a bitter falling out with his friend Tony Stark and comes to form an underground superhero opposition that pits one half of the Marvel Universe against the other.)
Downey's work as Iron Man has brought in big bucks for Marvel and Disney.
The three "Iron Man" movies have earned $2.4 billion worldwide, while the first Avengers earned a record-breaking $1.5 billion worldwide in 2012.
