I'm hoping she plays Rogue, and Carol gets attacked/decimated by Rogue, as was done in the comics. Larson didn't get rave reviews when she was cast, and her behavior off camera has had some controversies. Wouldn't surprise me if they were looking to make a change. It would thrill me if CM2 ended with Monica stepping up to the Captain Marvel identity, and Carol took a back seat. Maybe they could add Carol to the Guardians of the Galaxy cast as Binary.
I think it would be smart to introduce mutants gradually in other movies, so when the X-Men finally "Assemble", it feels like a bigger deal. So Rogue/Mystique in CM2, Quicksilver in WandaVision, Storm in Black Panther 2, etc etc.