While bringing Oscar-winning actress Foster to the superhero franchise seemingly won't be a problem, it is unlikely for 58-year-old Gibson to join Marvel film due to his infamous anti-Semitic rant, reported Aceshowbiz.
"Mel is a far different story. Marvel is run by one of the richest and most prominent Israeli businessmen in Hollywood, and you can be sure even if Robert got down on his knees and begged, there's no place for Mel in the Marvel films," a source said.
"Robert is very big into working with his friends. Ashley Hamilton and 'Iron Man 3' director Shane Black both credit him with making the final push to get them hired."
Downey became close friends with Gibson after starring with him in 1990's 'Air America'.
Downey defended Gibson during 'The Passion of the Christ' controversies and once said "nobody's perfect" in response to Gibson's DUI. In 2011, Gibson presented Downey with lifetime achievement award at American Cinemateque Awards.