I suspect that GT7 is already the Prologue of GT8, which could be released in 2024 or 2025, with all the glory of the PS5 hardware.
This excuse has been going for a solid decade now.
GT5 was just a prologue for GT6, which will fix all the problems. GT6 is just a prologue for a real next gen PS4 version - oops, we got GTS. GTS is just a prologue for GT7 which will be a real GT game again.
These were all full games in their own right. The prologue thing is just a way of making excuses for games that have great potential but aren't up to the standard that they should be.
If GT8 were to come out, what would differentiate it from GT7? Besides better graphics. Honest question.
Where would all the new cars and tracks come from?
I don't think you would need lots of new cars and tracks to make a meaningfully new game. I mean, it would be nice (and sort of expected) that there be new content, but imagine if you had to take just the tracks and cars from GT7 and make a game. What do you do?
-Massively expand and improve the career. Include improved AI, qualifying, and a range of difficulty levels.
-Massively expand and improve the online modes. Include both synchronous and asynchronous play, as well as daily/weekly/monthly challenges. Also, shuffle racing.
-Selling cars, obviously.
That's a good start right there, and done well enough would be worthy of an entirely new game. Going into the specifics of what an improved career or online would look like is a whole topic unto itself so let's just assume it's whatever you think would be really good. What else could we add?
-A proper course maker is a popular request. Include the ability to share online.
-An improved event creator would be cool too. Include an advanced mode with very granular control of AI and other parameters. Include the ability to share your events online.
-People liked the idea of B-Spec. Maybe a management sim on the side would be a more engaging way to do that?
-Endurance races where you actually do reasonable stints, and the AI takes over in between. You can watch the AI do it's stint if you want or just skip to your next stint. You can save in the pit stops and go do something else if you want, but no save scumming.
-Time/weather on
all circuits, including snow/ice where appropriate. Suitable tyres to be included.
I think you can do more than enough with the current content of GT7 to warrant the purchase price of a new game without adding any car/track content at all. It just requires some moderately difficult design work and the ability to iterate through builds and find what's fun. But that's video game design.