In fairness to the 4090, Cyberpunk 2077 at 4K, with all settings on maximum (plus all RT options enabled and lighting set to Ultra), is a complete slideshow on most hardware anyway. Just done some in-game testing myself, and on an i7-9700K + 2080 Super system, it averaged 1.5 fps with no DLSS. The only way to make it even remotely playable was to enable Ultra Performance DLSS, which resulted in an average frame rate of 46.The takeaway: It can't run 2077 maxed at 4k very well.
Obviously, one can't know exactly what section of the game Nvidia was demonstrating, but for the sake of comparable reference, I got 20 fps at 1440p, no DLSS, settings at maximum, RT at Ultra. To get similar performance figures (I.e 'just under 60 fps') took the use of DLSS Performance (52 fps) or Ultra Performance (70 fps), but the loss in visual quality just isn't worth it. DLSS Quality helps keep the pretties looking pretty, but not very playable at 11 fps.