The old adage goes, "where there's smoke, there's fire." In this case, where there are dozens of job listings for an unspecified project by a studio that just pooled all its resources to work on a single upcoming game, you'd best bet that development is in full swing.
Rockstar Games already confirmed that it has pooled all of its resources towards making Grand Theft Auto 6 "the best that it can possibly be."
We're not saying that the studio isn't working on anything else, but what other games can you think of warrant the appearance of dozens of job listings by the company? If you don't believe us, feel free to check Rockstar Games' career page as well as Hitmarker, a career website specifically dedicated to jobs in the gaming industry.
With a whopping 226 jobs at Rockstar posted within the past month, it's safe to say that the development on GTA 6 is well under way.