This is an interesting aspect too. RDJ hasn’t headed a Marvel film for 5 years, it’ll be 6 by the time Endgame comes out. He’s been there but with fewer stunts and effects work and screen time.
I remember after they announced that Man of Steel 2 wasn’t happening and JL was that Smith and Bernadin commented that Cavill could have stumbled onto the best career in films, no more ‘one for me, one for you’ but turn up for 6 weeks of a year to bank a paycheck for a supporting role and then do what you want anyway.
This is to some degree unprecedented. He may be sick to death and dies in the next movie but he may be happy getting a lovely pension for limited work for the rest of his days.