2K Sports released a 1:30 minute clip featuring the First Look to Current-Gen Gameplay. Not a great deal, no real difference if you compare NBA 2K20.
They announce updated shoes, career mode, but it's not too much taking into account that we are just a month ahead of the game release.
No big changes can be expected in the NBA 2K21 current-gen versions ( PC, Xbox One and PS4 ). All 2K efforts are geared towards the Xbox X and PS5 versions. In fact, it was announced by Mike Wang, 2K developer, that current-gen and next-gen version are being developed by two different studios.