Well,while GTS can achieve 4k the live events are not broadcasted in 4k,they have to cut some corners for the livestreams.
That is a question mark for me,with the consoles ditching the Jaguar CPU,the jump to next gen is expected to be pretty big and some hurdles this gen had because of the Jaguar system won't exist anymore next gen,i wouldn't be surprised if 8k is achievable next gen,this gen was capable of achieving 4k.But 120 FPS won't happen or it will happen in a really limited tech demo.
Also,the Ray Tracing that everyone is freaking out about won't happen next gen,PS5 won't have the RTX ray tracing cards,it's expected to use AMD cards.