So, MCU's phase three will be ending with Avengers: Endgame, Spider-man: Far From Home has already given us a glimpse of Phase 4 with thankfully a few familiar faces returning. Samuel L. Jackson's Nick Fury and Cobie Smulders Agent Maria Hill. But what fans want to know is what, how and who will replace Tony Stark and Captain America after Avengers: Endgame, because let's face it both actors can't carry on in their respective roles forever. No matter how much we would want them to.
Eventually, Marvel will have to consider replacing most of the original Avengers. And that includes Thor as well. Actor Chris Hemsworth seems to have moved on to a new franchise with Men in Black: International. But he has not explicitly said that he is done with Thor. Scarlett Johansson's Black Widow still has her solo movie.
So Johansson may still be a part of the MCU going forward. The Shield characters seem to be safe for the near future at least. It's the heroes that are not necessarily members of Shield that have an uncertain future.
Even Mark Ruffalo's Hulk doesn't seem to have a future except for the Avengers movies. Marvel is keeping tight-lipped about any future solo Hulk movies. And who can blame them. The past Hulk movies have left something to be desired. Hawkeye seems to be retired and his appearances in future Avengers movies are not known but it seems like Jeremy Renner too may be retiring his bow and arrow.
So, out of the seven original Avengers, only Black Widow seems to have any kind of future. The rest of the original members have an uncertain future. The new members of the Avengers like the Guardians and Spider-man are getting future movies. Doctor Strange for one, Captain Marvel and Guardians of the Galaxy will also be getting sequels.
They might tie into future Avengers movies. Maybe Tony Stark, Captain America and Thor will make appearances but may not be the prime focus, especially since Captain Marvel does become the leader of the Avengers in the comics. Maybe Avengers: Endgame will serve as a platform for Captain Marvel to take over from Captain America and Ironman.