We should see an improvement in game quality for the platform once last-gen sales drop off enough that developers only need to target current-gen.
Right now any game that comes out for both PS4+5 is bottlenecked by PS4 memory and performance, with only easy wins taken for PS5 like higher quality assets and faster IO/FPS.
Designing a game for current-gen platforms from the ground up is when we'll start to see some more impressive features, but there's still money on the table for PS4 so it'll be a few years (IMHO) before we see PS5 exclusives as the norm.