Over on GTA Forums an eagle-eyed fan has posted a screenshot of a resume belonging to a 3D artist that listed, among other jobs, a position as a "Jr vehicle artist at Rockstar games". The description of their work? "Create vehicles matching with real world for Gta5 dlc and upcoming Gta6."
Rockstar have yet to announce a sixth Grand Theft Auto game but considering how it sold it doesn't take a genius to figure there's a sequel in the works. This particular leak might not be legit, however. Previous leaks and announcements have turned out to be pranks, and even the forum poster responsible for highlighting this one has said, "In my opinion he is either trolling or this is some sort of mistake,there is no way a Rockstar employee would break NDA like that."