If that ends up happening, maybe Gunn could at least stay attached to Guardians of the Galaxy 3 as a producer.
However, as James Gunn said in his interview with Complex, whether or not he returns for the threequel hasn’t been decided yet.
Gunn has been the primary driving force behind these first two Guardians of the Galaxy movies as their director and writer, so it’s hard to imagine him not being involved in a third movie.
Although Marvel still hasn’t given any indication on when they’ll announce their Phase Four sale of movies, we know that Guardians of the Galaxy 3 will be one of them.