Just to reaffirm my earlier statement about the game only being as good as the PS4 Pro can manage, it looks like this may be the case.
In a recent interview with Phil Spencer, he acknowledged that there "may be" clauses that force parity of fidelity, but that he's fundamentally against it, of course because it would effectively cap some games on the 'X'. There's rumors floating around that Destiny 2 was capped at 30 FPS not only because of this, but also because the original XB1 needs to be given consideration.
Sony's Jim Ryan: http://www.vg247.com/2017/06/14/sonys-jim-ryan-isnt-worried-about-xbox-one-xs-power-game-devs-more-likely-to-aim-for-lowest-common-denominator/
Phil Spencer: https://www.gamespot.com/articles/e3-2017-phil-spencer-talks-xbox-one-x-potentially-/1100-6450916/
All in all, I don't suspect any platform really has any leverage to force this sort of policy with Rockstar, and in fact, it's Rockstar that calls the shots and maintains the parity.
.......please be a PC version on release, please be a PC version..