Perhaps. I can’t rule out completely the possibility of Lemmy stagnating. In that case as PieFed development progresses, and the feature gap becomes wide, more and more instances shift from one to another. I do think however the Lemmy devs won’t simply see their software being replaced without “fighting back” (in a good way).

A third possibility would be specialisation - PieFed and Lemmy still coexisting, but taking different niches.