
Variety claimed that Marvel Studios has a sequel "in development" for Phase 6's upcoming first movie. Having closed out Phase 5 with Thunderbolts* in May, Marvel Studios is preparing to begin the Phase 6 in July with The Fantastic Four: First Steps. The much-anticipated reboot will be followed by Spider-Man: Brand New Day, Avengers: Doomsday, Avengers: Secret Wars, and possibly a mystery MCU movie that will all help to round out the Multiverse Saga.
In a report covering a newly-added December 15, 2028 release date for a new MCU movie, Variety noted several "in development" projects at Marvel Studios that could land then, including a sequel to The Fantastic Four: First Steps. The revelation clearly demonstrates Marvel Studios' faith in Phase 6's first movie ahead of its July 25, 2025, release date.
After two attempts at adapting Marvel's First Family under Fox, the MCU is hoping to find luck with its all-new cast. The faces of the 2025 reboot include Pedro Pascal's Reed Richards, Vanessa Kirby's Sue Storm, Joseph Quinn's Johnny Storm, and Ebon Mass Bachrach's Ben Grimm.

Fans will meet the MCU's four newest heroes when The Fantastic Four: First Steps hits theaters on July 25. It's too soon to tell when a sequel could arrive, but Variety indicated it could take one of the mystery 2028 dates.
Those 2028 dates are scheduled for February 18, May 5, November 10, and December 15, but it's too soon to tell when The Fantastic Four 2 will land. That decision will depend on the first movie's success, how sequel development progresses, and the actors' schedules.
The Fantastic Four 2 Might Be Very Different - Here's Why

Marvel Studios has recently gotten some shtick from fans for waiting so long between sequels to beloved movies. For instance, four years have gone by since Shang-Chi and the Legend of the Ten Rings with no signs of a sequel coming anytime soon, despite receiving strong reactions in the pandemic.
As Marvel's First Family is one of its most popular heroes and their MCU debut is bound to be a box office success, it's only right to start work on a sequel early to keep the wait minimal. That said, it's too soon to tell if it could grab one of the studio's four mystery 2028 release dates.
The Fantastic Four is set to take place in an alternate retro' 60s-inspired universe before the team comes to Earth-616 in Avengers: Doomsday. As the Multiverse Saga ought to end with the Fantastic Four in the same universe as the MCU's main heroes, the sequel might see some big changes.
Most notably, the Fantastic Four will presumably operate in the same universe as the Avengers and the new, rebooted X-Men team. This could prompt an interesting fish-out-of-water story in which the Fantastic Four have lost their celebrity status and are living in a very different world.