Tagged as rumor despite Lance's credibility just in case, but it seems pretty likely that at least for some games it will work like this. Interestingly enough, one of the replies seems to suggest that Dark Souls 3 won't hit the 60FPS mark on PS5:
Unsure about DS3, but Sekiro was one game that went up to mostly 60FPS on Series X through BC without any optimization on the From side of things, so it's disappointing if the same isn't the case on PS5 at least for some games.