This market resolves to the Metacritic score of the next entry in the mainline GTA franchise, one week after the release date.
If it is released for multiple platforms, this market will resolve for whatever platform it was released on first. If it is released on multiple platforms on release day, this will resolve to the average score among them, rounded.
I am no fan of GTA -- I haven't played them, I hated "Red Dead Redemption", and indeed I actively dislike Rockstar as a company and what their games seem to represent. But face the facts, people: basically every GTA and Red Dead Redemption game since in 2002 has scored over 90 on metacritic. (That's 3, Vice City, San Andreas, 4, Chinatown Wars, and 5, plus the two Red Deads: https://www.metacritic.com/company/rockstar-games?filter-options=games&num_items=30&sort_options=metascore&page=0). Even freaking LA Noire somehow got a metacritic score of 89!! Only anniversary-edition re-releases, multiplayer online modes, and random DLC packages have scored less than 90. I don't know what it is that people love about these games, but Rockstar has evidently got a formula that works.
So you have gotta figure that even if GTA 6 is a comparative dud, surely it will at least hit 85 or so. Compare also to Cyberpunk 2077, which (despite an infamously disastrous, bug-ridden launch) got a score of 86: https://www.metacritic.com/game/pc/cyberpunk-2077
