There's really nothing that prevents Pike from being promoted to Fleet Captain while still retaining command of the Enterprise. So there's wiggle room there.
Hell, for all we know, Pike could already be a Fleet Captain - AFAIK, that's not a distinct rank, more like a Captain with additional responsibilities.
Remember, this is still the prime timeline. There haven't been any changes. So the Pike from "The Cage"/"The Menagerie" has the same knowledge of his future that Anson Mount's Pike has.
Hell, for all we know, Pike could already be a Fleet Captain - AFAIK, that's not a distinct rank, more like a Captain with additional responsibilities.
I think Pike's foreknowledge of events will see him promoted to Fleet Captain a bit earlier
Remember, this is still the prime timeline. There haven't been any changes. So the Pike from "The Cage"/"The Menagerie" has the same knowledge of his future that Anson Mount's Pike has.