The problem for Marvel is that Fantastic 4 is the only movie left between now and the next Avengers.
I still think the next Spider-Man will do well, just like Deadpool 3 and GotG 3 did. People want to see the continuation of their favorite characters, they just won't show up for everything Marvel like they used to.
I think after Doomsday/Secret Wars, the main focus of the MCU will be on X-men, the Fantastic Four and Spider-man. I count Deadpool as being in the X-men corner of the MCU.
So the question remains...what happens to all the other characters that were focused on in Phases 4 and 5?
I think the Wanda can continue to be a major presence in the MCU, especially since at various points in the comics she was Magneto's daughter. This was retconned, but I think the MCU could use this angle to tie her into the X-men side of the MCU. She might even be able to get her own movie. Doctor Strange probably could also get a third movie to round out his trilogy.
I think Thor could have more sequels if they go for a different tone than Love and Thunder and try to strike a better balance between seriousness and humor.
Shang-Chi should also get a sequel. While the first film only made $432 million worldwide, it was well liked and its relatively box office was due to the pandemic. I think a sequel has potential to break out and make much more money. Maybe they can pair Shang-Chi with other characters tied to the mystical side of Marvel (like Doctor Strange).
I think the Black Panther franchise can have future sequels, but they need to recast T'challa as I don't think Shuri or T'challa's son will have quite the same appeal. After Doomsday/Secret Wars they can bring in a variant of him.
I personally loved Eternals, but I know most don't so I don't think Marvel can give them a sequel. It would be too financially risky. Unfortunately, the movie ended on a gigantic cliffhanger with half of the Eternals kidnapped by the Celestial Arishem (who threatened to return to earth for Judgement) and the other half running into Starfox, the brother of Thanos, who said he knows where to find the kidnapped Eternals. I think there is a way to tie up the loose ends brought on by the cliffhanger of Eternals without necessarily giving them a sequel. I think they could have "cosmic Avengers" type team up movie where Thor, the Fantastic Four, the remaining Guardians of the Galaxy, and Thena, Makkari and Starfox join forces to stop the Celestials from destroying earth. It would be less of an "Eternals 2" and move of an "Avengers Age of Ultron" scale crossover movie. Afterward, I think the Eternals as a group should disband. Maybe one of them could join the new Guardians of the Galaxy and one or two of them could join the Avengers, but I really don't see the point of them existing as a team anymore going forward.
Sam Wilson's Captain America and Brie Larson's Captain Marvel are not popular enough to get any more solo movies going forward. I don't think they should be written out of the MCU, but I think they should only be present in Avengers movies, as supporting characters.
I think the Young Avengers (who have been popping up throughout phases 4 and 5) should be given a TV series, not a movie. There is potential in these characters, but they are not popular enough to sustain a $250 million movie. I also think since several of the characters were introduced on TV (Kate Bishop, Kamala Khan, Billy Maximoff/Kaplan) TV is the natural way to continue their stories.
I think Moon Knight and DareDevil can live on as TV characters, but don't see them successfully transitioning to the big screen. Echo and Secret Invasion should just be quietly forgotten about.
She Hulk was an extremely divisive show and a nightmare in terms of online culture war discourse, although its viewership was solid. Still, I think Tatiana Maslany was well cast and the character still has potential. But the writing of the first season was all over the map. If the show were to ever get a second season, I think they would need to completely overhaul the creative/writing team.