I fully expect this to happen. And it makes no sense - considering everything that's happened with the Avengers vs the Phoenix or Jean returning then turning her back on the X-Men. But I can absolutely see an executive meeting where it's decided that Phoenix joins the Avengers right in time for the Dark Phoenix movie.

It also seems like editors aren't going to greenlight bringing back characters if it's not for a major story and a writer that says I want Jean/Scott/Logan/Prof X and this is the plan for them.