I'll eat my shirt if Strange brings mutants in. That entire "theory" is just people hearing "multiverse" and knowing Fox was just bought up by Disney and leaping to UTTERLY unwarranted conclusions.
Such obviously bad conclusions Wandavision trolled them with Evan Peters' casting, and then very obviously made him clearly no one important.
We
may get some burst of energy that causes mutations, but the cast of the X-men films are almost certainly
not showing up as those characters, ever.
As for Spider-man, assuming you meant "
No Way Home", since FFH already came out a couple years back, we know Foxx and Molina are reprising Electro and Doc Ock, but nothing about the
rest of the Sinister Six. Even the two of them in one film is more than enough.
The idea of a Storm cameo in Black Panther 2 is literally just X-men fanatics desperately hoping for X-men to be part of the MCU, and again, there's zero indication that's happening. And even if some show up, almost certainly gonna be recast, and probably with fresh origins.
And the idea that they're phasing Carol Danvers out is just baffling. Must be the same people who kept claiming Captain Marvel was a flop and nobody liked it, when that movie made over a billion dollars. She's one of their most bankable characters, especially given that not counting Avengers team-up films, the only solo-character films to top that were characters that were retired (Tony Stark, Steve Rogers) or whose actor passed away (Boseman). Captain Marvel pulled more in than any Tom Holland Spider-man, any Thor film, any Ant-man, etc.
Plus, we
know what her next film is;
The Marvels. Also starring Monica Rambeau and Kamala Khan, as introduced in Wandavision and the upcoming Ms. Marvel Disney+ series. So whoever made that claim is just pulling a phenomenal ass-pull based on personal issues they have with the character for some cockamamie reason.