We've known for some time now that Robert Downey Jr. and Chris Evans will likely be hanging up their Iron Man and Captain America suits soon. They've been running around saving the world for 10 years now, so it's about time they moved aside to allow some youngbloods to take up the task. Post-Avengers 4 would be a perfect opportunity for Kevin Feige to do so, considering so many of the original Avengers are coming to the end of their deals with Marvel.
The fourth Avengers movie will tie up the last 10 years of MCU filmmaking to welcome in that transition and will likely pave a path for Tony Stark and Steve Rogers to depart, as well several other members of the team. Mark Ruffalo seemed to hint at the Hulk's "final exit" on Instagram in February, though he does has one more film left on his contract (likely to be Thor 4). Scarlett Johansson is coming to the end of her contract too, only confirmed as the lead of a long-awaited solo Black Widow movie.
This leaves a gaping hole to be filled by a new generation of Earth's Mightiest Heroes, and with Captain Marvel set to be the face of the MCU's Phase 4, she might be the perfect person to lead a new team of Young Avengers. Carol Danvers has a rich history with the Avengers in the comic books, since the 1970s, when she was running around as Ms. Marvel, all the way through to storylines in The Mighty Avengers, Secret Invasion, and Avengers: Assemble runs of the 2000s.
Tom Holland has been a very welcome addition to the MCU and has proven to be a worthy bearer of the Spider-Man mantle, though he hasn't really done too much as an official Avenger yet. At the end of Homecoming, he realized he was a bit young to join the team full-time, and in Infinity War nearly every superhero ended up being an Avengers team member, but future movies could see Peter Parker play a more central role.
The same could be said for everyone's new favorite Disney princess, Shuri. Letitia Wright has breathed new life into the MCU by being not just the smartest person in the room even when the Science Bros are there, but also one of the funniest too. With Tony and Bruce likely to be retiring, the Avengers need a brilliant new mind to come up with the team's new tech, and the teen genius is decades ahead of Stark Industries when it comes to innovation. Shuri is not just a brilliant mind, she's a fighter too — she held her own pretty well during that final fight scene in Black Panther, and with her own weapons to wield she'd be a worthy addition to the Avengers line-up.
New York has often been the base of operations for the Avengers team, and with the confirmation that Ms. Marvel is going to be entering the MCU mix, there's another local superhero to join the ranks. Kamala Khan's origin story is heavily linked to Captain Marvel; she literally turns into a young Carol Danvers when the Terrigenesis process awakens the Pakistani-American teen's powers because she was thinking of her favorite hero at the time. Captain Marvel thus becomes a bit of a superhero mentor to Ms. Marvel, and the latter does eventually join the Avengers too, so it would be pretty epic to see the two share the big screen and continue that relationship in a new Avengers movie.
Captain Marvel, Spider-Man, Shuri, and Ms. Marvel are a pretty good start to a younger Avengers line-up that would see these superheroes become as legendary as their predecessors as well as welcome in a new, more progressive era for the film franchise. The original Avengers focused on five white heroes, only one of them a woman, and over the years their ranks have barely expanded to include more diversity. Black Panther has proven there is an appetite for films that offer a wider perspective than the white hero factory settings the MCU had been stuck on, and a Young Avengers line-up led by a woman — who also happens to be the most powerful hero ever in the MCU — and featuring a brilliant black woman and a magnificent Muslim girl would really show that Marvel is taking its diversity push seriously.
The top three highest-grossing films of 2017 were led by women, one of them by a superpowered woman, so it's clear the viewing public is ready to put their dollars down to see the ladies lead the way. If Disney boss Bob Iger is serious that the MCU will possibly see more Avengers down the road, then it should head in a Young Avengers direction.