The MCU slate is never "locked in."
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Things happen, such as the Spider-Man deal killing Inhumans (though their use in the SHIELD tv show also contributed).
This is the announced slate:
Spider-Man: Far From Home (7-5-2019)
Untitled movie #1 (5-1-2020)
Untitled movie #2 (11-6-2020)
Untitled movie #3 (2-12-2021)
Untitled movie #4 (5-7-2021)
Untitled movie #5 (11-5-2021)
Untitled movie #6 (2-18-2022)
Untitled movie #7 (5-6-2022)
Untitled movie #8 (7-29-2022)
These movies are locked in:
Spider-Man: Far From Home (7-5-2019)
Black Widow (5-1-2020)
The Eternals (11-6-2020)
Black Panther 2 (2-12-2021)
Doctor Strange 2 (5-7-2021)
Black Widow and Eternals are filming this year. Black Panther 2 and Doctor Strange 2 are unlikely to move. Especially considering Fox Marvel characters will need scripts, directors, and casting.
This is the first spot things could change:
Untitled movie #5 (11-5-2021) — Likely Shang-Chi and they’ve already hired the director. This movie will likely make massive amounts of money in the Asian markets, which we don’t always consider, but there’s financial reasons they’re elevating a character most people in this country don’t care about.
Untitled movie #6 (2-18-2022)
Untitled movie #7 (5-6-2022) — Likely Guardians 3 based off when Gunn should be finishing up Suicide Squad 2.
Untitled movie #8 (7-29-2022)
So you have two open spots there. Movie #8 will almost 100% be Spider-Man 3 unless Sony doesn’t re-up. Leaving movie #6 to be a Fox Marvel property or Captain Marvel 2, Ant-Man 3, Thor 4 (if he lives). I’d bet on Captain Marvel 2.
It doesn’t mean they won’t soft reboot them throughout these movies. The Strange 2 director tweeted out a picture of Strange with Namor. His movie rights are tangled up with Univeral similar to the Hulk. He’s Marvel’s version of Aquaman, but also considered a mutant.