I never said 4K/60fps won't be possible, but most AAA games will not run at that spec. It's not as simple as just making it 1080p, you'd also have to slice CPU processing time to 1/4 of a 30fps game, so only simplistic games will be able to be 120fps.
Read Dead Redemption 2 an open world games that look like The last of Us or even far better, is a triple A games run at 4k 30 fps on Xbox One X. I bet triple A games will not just run at 4k but will able run games at 60fps on PS5/Scarlet easily. It depend on how the graphic fidelity and the visual quality of the games.
RTX 2070 mostly run games at 1440p 60fps at ultra setting. PS5 and Scarlet will have equal or better than RTX 2070 and have low level API and far better optimization . It will safe to say 4k 60 with current graphic fidelity on PC in ultra setting is possible for PS5 or Scarlet.
Also if you games with high refresh rate monitor (up to 144 hz) using RTX 2070 , RTX will able to run games like Overwatch in 1080p at 144hz . PS5 and Scarlet also will be using ryzen 2 CPU, so no more bottle neck by Jaguar CPU.
PS5 and Scarlet will be on par or slightly more powerful than RTX 2070. keep in mind RTX 2070 will be a mainstream cheap GPU on 2020 , so 4k 60 or 1080p 120 fps will be the norm for console gamer or budget PC gamer.