Exactly, so are all computer graphics look at how far we've come from CGI in movies from 10-20 years ago. Techniques get passed down and technology moves on. We are nowhere near photo realistic graphics. Just look at the art and animations created in blender its astonishing like real life in some cases.
Anyway watch the below video, its a good explanation to what photorealism means today.
Simple answer yes we already here , those graphic can now be produce on PS5 and Xbox series X . Also the answer is the lightning , to be proper photorealism it required real time lightning based on natural light A.K.A Ray Tracing. And yes we now have RT on next gen. So PS5 to PS6 will not be about photorealism i assume. There are other thing to make game realistic beyond photo realism, which are animation , AI, Physics , weather, living world etc.