You know, if you look at some of @EoinOBroin work here: Striving for Photorealism in UE4 - Work in Progress - Unreal Engine Forums, it almost appears that games can already achieve photorealism. I don’t know how his scene’s perform however, or what kind of hardware you would need to support them. From what I can tell he only uses skylights and directional lights to light the scenes, nothing out of the ordinary. How much of an improvement is ray tracing actually going to make compared to what Unreal can already achieve? It makes me think that real time Ray Tracing isn’t as exciting as it’s made out to be.
Now granted, he uses assets from Megascans, which, your lighting can only be as good as your materials, so I’m sure that’s part of it.