We all saw the matrix demo, and that it dips below 20fps when lots of stuff is happening, thats max for xsx/ps5, limit that wont be reached in actual game, coz even in fidelity mode actual game cant dip below 20fps, but gotta hold at the least mostly stable 30.
Gta6 will look good, but best case scenario will be close to the matrix demo, lets see game's actual gameplay trailer(not cinematics/in engine aka bullshot trailer, we always get those and actual gameplay looks always much worse), then we can somewhat know what to expect from final game, at least on consoles.
One positive thing is, since rumors/leaks about ps5pr0 coming holidays 2024- will be just in time for gta6, that definitely gives gta6 ps5pr0 version potential to shine.