The PS4 can't even play every game at 1080p60.
PS4 exclusives are 1080p 30 fps on the base console and go upto checkerboard 4K 30 fps on Pro. We know Pro is bottled by its weak CPU and its lack of memory.
PS5 is supposedly going to have Ryzen CPU and a GPU 3 times more powerful in terms of teraflops, with a more modern architecture and with 16 GB of RAM atleast as Xbox One X already has 12 GB. The suggested specs should easily run PS4 Pro games at twice the resolution, as checkerboarding halves the resolution on one axis and twice the framerate, which is fairly easy since the GPU is hugely powerful and even PS4 Pro's weak CPU can run some exclusives at 1080p 60 fps. The 16 GB RAM will allow 4K textures. I'm certain PS5 will be capable of doing this if these are the specifications, but of course Sony needs to allow its developers to upgrade their games on PS5.