Going by Quake II RTX vs Quake II OpenGL, it probably wont work very well.Doom Eternal's engine using path tracing. You just know that would be amazing, an engine that is optimised to 100% and scales on literally any hardware. That would be a true test to see how demanding just RT is in a game engine, as don't think there is any other modern engine that is as efficient and scalable than Doom Eternal's. We already know that you can get over 150fps in Eternal with RT enabled without enabling any DLSS, so would be super interested to see how path tracing does in it.
Quake II, 3440 x 1440. 3090 Ti 5800X3D
RTX - 84fps
OpenGL - 2094fps
So about 25x the GPU power needed for RTX. Might be totally wrong of course, this is just guess work based on RTX in Quake II
No doubt the next biggest things in GPU development will be newer version of DLSS and AI frame generator chips or something to boost framerates instead of making a GPU that you plug directly into the mains and runs at 1000W!