While I wish this to be the case, GTA: 0 makes Rockstar ridiculous amounts of money, and I don't see the trend stopping with the release of GTA 6.
Sure, the smaller number of platforms that can run it will impact sales, but the product will be profitable in the long term. GTA: O was earning Rockstar $500 million a year back in 2022, nearly a decade after GTA 5 first launched.
Sales of copies, sale of GTA: 0 expansions, Shark Cards et al will ensure they'll recoup development costs in a few years.
Here's the sticky part for R*, every GTA

player that moves to GTA6 is lost profit unless that user spends more on GTA: online 2. To do that, you have to ramp up the price of the gatcha.
Will GTA:6, launching to fewer customers, on a more expensive platform, as a more expensive game, with more expensive gatcha, work on enough people for GTA:6/O2 to be profitable quick enough for it not to be a flop?
Will those people hang around for a decade like they did with GTA 5?
While GTA relies on the name and previous entries to sell people on GTA6, there are more variables that say GTA6 will fail vs being a success.
Define fail. It definitely won't exceed or even match GTA5, hell, it probably won't even be THAT profitable considering how long they've been sitting on a sequel, but there's almost no chance it doesn't turn a profit. Probably a generous profit at that, just nothing crazy.
Fail = not meeting expectations. People think it will sell a bajillion copies (it will) and will score 10/10 (bought reviewers will ensure it does) and be a yuge success.
Yet all it takes is enough distasteful pandering, overly-woke shite or, the biggest killer of all, for the game to be a bit bland and boring and it's dead. Servers will crash, the game will be unplayable for 24-48 hours and while that's never killed a game in the past, it won't start the game on a positive footing.
It won't turn a profit for a long time. It would need to sell 30 million copies (not including Sony's cut) just to turn a profit.
It's not out of the realm of possibility, but when was the last time a game sold 30 million copies in a year or a quarter?
The success of GTA6 will be measured by the time it takes to get a PC port. 12 months means it's on track, 18 months means it's mega successful, <12 months means it's struggling, <6 months means it's fucked.