Variety was reporting that this may take like 12-18 months to pass through regulatory bodies (It's a huge merger with both companies owning a ton of stuff, on top of it flipping potential monopoly warning signs) There's even the possibility of it not clearing regulation, though with this administration, that feels a lot less likely. (Apparently Trump actually called Murdoch to make sure Disney wasn't purchasing Fox News. Good lord.)
So New Mutants, Deadpool 2 (They still haven't officially named this yet?) and Dark Phoenix will probably all come out, but I bet that's it. I'm pretty sure that Gambit movie is not gonna happen now though. Maybe. It's like the cockroach of comic book movies; nobody seems to be able to kill it.
Adding the F4 to the MCU is pretty easy to have as having always been part of the universe. Skip the origin, it's super easy to explain in 30 seconds (did a space experiment, got hit by radiation, got superpowers. Ben is sad.) and just say they've been laying low after the accident, dealing with stuff like cosmic shenanigans, the negative zone and alternate dimensions to explain where they were during, say, the Battle of New York or Infinity War.
Adding the mutants is a huge can of worms without pulling a colossal universal reset. Either guys like Magneto, Xavier and Wolverine have been sneaking around as mutants for decades and nobody noticed, or those characters will have to be radically reimagined. It'd feel real crappy to do a housecleaning film like Days or Future Past or what DC is rumored to be doing with Flashpoint. (Basically making a film who's entire point is to explain how previous movies or events no longer count or are different.) but maybe they could do a 2015 Secret Wars inspired film where multiple universes are pitted against each other and the MCU and a mutant universe (either the existing film one or a new one made from scratch) wind up merged into one universe at the end. That still feels weird, though.
Honestly, I think the biggest effect we'll see is Marvel Comics will stop treating the F4 like they don't exist, and Marvel licensing will be able to acknowledge X-Men characters again.