(Image Source: Marvel Studios)
Recent Marvel movie plot rumors have largely focused on "Avengers: Doomsday." However, in recent days, plot leaks for "Avengers: Secret Wars" have also begun to surface more frequently, gradually revealing a rough outline for the upcoming film.
Sources for these recent revelations include well-known scoopers and media personalities such as Daniel Richtman, Cryptic HD QUALITY, and Alex Perez, editor at The Cosmic Circus. Below is a plot description compiled from their reports.

(Image Source: Marvel Studios)
According to their claims, most characters with significant roles in "Doomsday" will see their screentime drastically reduced in "Secret Wars," relegated to almost NPC-like status. This is because they will have been brainwashed and manipulated by Doctor Doom, completely losing their past memories. Their roles are only expected to expand in the film's third act.
Conversely, characters with minimal screentime in "Doomsday" will have expanded roles in "Secret Wars." These prominent characters will primarily be the younger generation of superheroes, including Ms. Marvel, the second Hawkeye (Kate Bishop), and the third Ant-Man (Cassie Lang). However, they will also be led by several more seasoned, older heroes. Currently, Marvel Studios is reportedly considering potential candidates such as Wong, Star-Lord, Vision, the second Ant-Man (Scott Lang), Agatha Harkness, and certain as-yet-unidentified mutants. They will unite to resist the main antagonist, Doctor Doom, who creates Battleworld to control other heroes.
These outlets also indicate that Marvel hopes the nascent generation of young heroes, who haven't fully come into their own yet, will truly shine and establish a solid foundation in "Secret Wars." This is because these young heroes are also slated to lead the next generation of new heroes in the future.
via: ComicBookMovie