Contrary to belief here, I think he'll stay. Especially if Ronaldo has a good season and stays on for next year.
Firstly, I think he'll get games because Ronaldo cannot and will not be starting every game. Also, Cavani's fitness record is iffy at best and Rashford will play where he always plays; the left wing. Secondly, the player to leave in the summer will be Cavani who's contract expires. While Ronaldo is here, I don't see us splashing big on another striker like say Haaland. Because it's not needed, it will cause too much competition up top and probably even hamper the development of mercurial talents like Greenwood by restricting their playing time. The latter I expect to keep playing on the right for the foreseeable, especially while Ronaldo remains here.
So unless someone comes in and pays a lot to us and to him to take him off our hands, I expect him to go into next season as our second striker behind CR7. Fingers crossed he'll also find some form and prove useful to us this season.