Electronic circuits can no longer get so much faster than they are now, but the shift from raster to neural rendering should boost graphic capabilities to some unknown extent. Even now we're halfway there already with frame generation and deep learning upscaling.
But I think it's more a question of 'how long it takes to develop' rather than 'how good games can look' right now, to be honest. I'm sure if you could spend ten years polishing a PS5 game it would look like a PS6 title already, but that's not viable.