Rockstar's GTA Online is one gaming's most successful online services ever, to the extent that Grand Theft Auto 6 does not need its own version when it releases. GTA Online has already been active for nearly eight years, and recent updates like Los Santos Tuners (which pulled in more players than any other GTA Online update to date) have proven that the game's player base is still alive and kicking. When GTA 6 launches, even if it's in 2025 like current rumors suggest, GTA Online will likely still be popular thanks to upcoming PS5 & Xbox Series X updates.
Grand Theft Auto, as a franchise, are games centered around single-player experiences. While Rockstar had begun to experiment with introducing open world multiplayer antics to the series as early as Grand Theft Auto: San Andreas, it wasn't until GTA Online the company really found their footing - thanks in part to advancements made in games like Red Dead Redemption, which had its own online functionality years before Red Dead Redemption 2 would introduce Red Dead Online. Now, although there are still likely plenty of players who ignore these modes altogether and focus on Rockstar's single-player story content, it is GTA Online which has continued to receive ongoing support in the form of post-launch DLC.
When Grand Theft Auto 6 releases, Rockstar has a few different options for how it could approach merging this new game with the massive audience of GTA Online. There have been rumors which suggest GTA 6 could be a smaller experience at launch than players are used to, with more content being added though DLC over time. While the idea of a constantly updating, ever-changing world is one that many game companies seem to be moving towards (such as Ubisoft's Assassin's Creed Infinity project) it would make much more sense to simply let GTA Online evolve separately from the main Grand Theft Auto series - something that has almost started happening with purchasable standalone versions of both GTA Online and Red Dead Online.
GTA Online Has Grown Too Much To Be Contained By GTA 6
In the past year players have seen Fast & Furious-style street racing circuits, new vehicles, and even an entirely new island heist location (Cayo Perico) added to Grand Theft Auto Online. No matter where GTA 6 will be set, be it Vice City, San Fierro, or some other as-of-yet unseen Rockstar parody location, GTA Online players will not want to lose the progress they have made in the game simply because a new iteration came out. While another four years in development will likely mean the mechanics, graphics, and gameplay of GTA 6 will be far superior to what is currently on display in GTA Online, that doesn't mean those players should be left behind, nor should their achievements be discarded.
The best thing (and the most likely thing) Rockstar could do is make Grand Theft Auto 6 a completely separate experience from GTA Online, focusing on single-player antics in a new sandbox like fans expect while also updating GTA Online's servers to match and include the new game's features as much as possible. GTA Online players should still be able to visit their business and clubs in San Andreas (if they previously purchased a copy of GTA 5 or GTA Online), but should also be able to take a plane to GTA 6's location to engage in new activities. By including both Vice City, or wherever Rockstar decides to set GTA 6, as a possible but (crucially) optional location for GTA Online players to visit, it would allow them to both enjoy the new game's setting while also not losing anything they worked hard to achieve over the past decade.