I will just say that you need to look CGI thread to see how much of a jump we are going to have.
Sure every gen the jump seem smaller because there is the ceiling (that we will still take decades to achieve) but sure everytime we get nearer there is less road to cover. But it is still very noticeable. And I'm not even thinking about the bad stuff like pop ups, collision and things like that.
I have seem the CGs from FF7 and I can still easily see the gap. Even if my relatives when I'm gaming ever since PS3 ask if I'm watching a movie.
Once we really achieve photorealism we will still have other stuff to achieve. We are at something similar to people going from B&W tv to color tv thinking they didn't need anything more and it wouldn't be possible to improve that 21" CRT because they were already seeing images that were life like.
Yes we will have big jump, but from PS5 to PS6 i doubt we will see another jump. I am talking about general evolution onward. Also what lacking in this gen is just Ray Tracing , the rest requirement for photorealism already been achieved (like physically based rendering) . So if next gen (PS5) can achieve RT then we already in the realm of photorealism.