Rockstar has sold nearly 110 million copies of GTA 5, which makes a sequel very likely. Red Dead Redemption 2 was released on consoles late 2018 (we're still hoping for it to arrive on PC). Given that Rockstar's recent blockbuster games tend to land four-to-five years apart, that puts a GTA 6 release date at 2022/2023, assuming GTA 6 is the next project and not Bully 2 or Rockstar Table Tennis 2.
That will be well into the next console generation, so chances are Rockstar is developing their next big game for powerful future tech. At the moment there are very few specifics out there, but the Housers and other Rockstar devs have spoken in roundabout terms about the GTA series generally—maybe we can tease out a few clues.
It seems that the game definitely exists in some form. Recently GTA 6 was listed on an artist's resume working out of India. Rockstar has acquired another large studio in India from struggling Starbreeze, which suggests that Rockstar is staffing up on art resources for its next big game. A seemingly official in-game announcement saying that GTA 6 was due out in 2019 turned out to be fake, however.
Beyond a release date the most important thing we want to know is where (and when) GTA 6 will be set. Everything flows from Rockster's choice of city and decade. GTA 5's return to Los Angeles sets us up for a return to Vice City. In an interview with Develop in 2013, president of Rockstar North Leslie Benzies referred again to Rockstar's trifecta of preferred GTA cities
“We don’t know what GTA 6 will be, but we’ve got some ideas. We’ve got about 45 years’ worth of ideas we want to do. We’ll pick the right ones. It comes from the idea first. Where it is going to be set is the first question. That then defines the missions; you’re doing different things in LA than in New York or Miami. The map and story get worked up together, and the story is a basic flow of how it works out so you can layer the mission in."
Speaking of old GTA cities. A few years ago a Liberty City scene appeared on a Rockstar dev's profile, apparently mocked up in GTA 5's engine. This could easily have been a technical test, or perhaps a scene from some scrapped singleplayer DLC, but Rockstar once talked about putting all of their cities into one mega-game. That sounds absurdly ambitious, but Rockstar might well have the resources to do it.
Alternatively, back in 2013, Dan Houser suggested that there's still some interest in London as a setting, even if it doesn't end up being part of the Grand Theft Auto series. Speaking to the Guardian, Houser said: "I think for us, my gut feeling is, GTA London was cool for the time, but games were more limited then. These days I think we would love to set a game in the UK, set in London, whatever, but I don't know if it would be a GTA game. I think there are plenty of great stories we could tell about the UK, great environments to showcase, great gameplay mechanics that could have a UK bent to them—I just don't think it would be a GTA necessarily."
All of which is to say: who knows? In another interview Houser opened up the possibility that a new GTA could be quite different in tone and setting to previous entries, though it's hard to imagine the series moving away from the USA. “At the moment, it feels like GTA’s DNA is contemporary-ish, American-ish, English-speaking-ish, because that’s what it has been," Houser tells Polygon. "But that doesn’t necessarily limit it to those, that’s just what we’ve done so far.”
There have been more fairly spurious rumours around GTA 6. The Know cites an inside source that puts the GTA 6 release date as 2021-2022. The rumour suggests that the new game will be spread between Vice City and South America. A wild Christian Today rumour round up guesses at a 60s London setting and time travel. Comic Book gave credence to an anonymous since-removed pastebin post claiming that GTA 6 will feature multiple big cities connected by a vast stretch of land featuring smaller towns. In this version the player starts out as a small crook and ends up running a drug-running criminal operation.
It does seem likely that there will be at least a little bit of crime in GTA 6. Our money is on Vice City with an expanded version of GTA Online, which has been remarkably successful for GTA 5. Whatever GTA 6 is, hopefully we'll see it release PC alongside consoles this time. If you're still enjoying GTA 5, check out our guide to the fastest cars in GTA Online, learn how to make money in GTA Online, or just install some of the best GTA 5 mods and become the Incredible Hulk.