Reeves officially is done with the Planet of the Apes franchise, having concluded War for the Planet of the Apes, and he does not have an announced project on this slate.
This means that his next movie easily COULD be the Batman movie… though right now, that movie doesn’t have an official release date.
All of this is to say that whatever rumor John Campea brought up in the first place — whether there’s even a rumor at all — is not about Matt Reeves leaving the solo Batman movie.
His tweet has a Bat, and a thumbs up, which we take to mean that he’s still writing his script at the moment, and plans to direct.