I wonder if something similar to UE5 Nanite mesh could be utilised in SU in the future?
Mathematically, since future is approximately infinite, certainly yes.
Very good… but don’t give up your day job?
Not likely, since it is proprietary to Epic.
FWIW, one could argue that the Trimble trimbim format acts in a similar way, since it also manages geometry in conjunction with the distance to the camera, which makes it possible to have high details when zooming in.
The result is that one can view large detailed models even on lower spec devices like phones and tablets
Trimbim format is for viewing only, though, no editing.