If you head on over to the official Terms of Service page and scroll down to Section 10, specifically, "10.1 Availability.", there's a new part there that mentions Rockstar may offer "Specific Services" and that they could be a "part of a playtest, early access release, or other similar offering (an "In-Development Service").
The succeeding sentences are basically Rockstar's way of saying that they may offer a beta test or early access of a future title, the first of which could be GTA 6 or perhaps its online counterpart.
What's interesting about this particular change is the recent rumors about Rockstar's plans to turn GTA into the next metaverse, with insiders claiming that the studio met with creators on platforms like Fortnite and Roblox ahead of the game's release later this year. It's also worth noting that another insider claims that Rockstar is considering dropping numbered installments entirely, instead focusing on turning GTA into a live-service title for the foreseeable future.
If there's any truth to these claims, Rockstar will inevitably have to hold beta tests or early access runs on a regular basis, perhaps even taking advantage of the GTA+ subscription service to monetize it.
This wouldn't be the first time that Rockstar has given early access to one of their titles to a specific group of people. Previously, Red Dead Online, which is the online component of Red Dead Redemption 2, became playable for owners of Red Dead Redemption 2's Ultimate Edition 3 days early back in 2018.
We could see something similar with GTA 6, except this time it could be more exclusive if not extensive. This could even tie into the rumors that GTA 6 could sell for $100, which might include early access to the game and perhaps even a GTA+ subscription.
Given how popular Grand Theft Auto Online remains, there's no reason for Rockstar to hurry up with a replacement anytime soon. Take-Two Interactive even previously confirmed that they plan on supporting GTA Online even after GTA 6 hits the storeshelves later this year. So a potential scenario is a three-day early access to GTA 6 and a GTA+-exclusive play test for the rumored project ROME.
All of this is speculation for now and we'll have to wait for Rockstar to confirm anything, which might not happen anytime soon. Hopefully, with the release of Grand Theft Auto 5 Enhanced on PC on March 4, the runway is clear for Rockstar to put Take Two's increased marketing budget for the next fiscal year to good use and start dropping more official details regarding GTA 6.
Speaking of GTA 6, an anonymous developer recently deactivated their account on Reddit where they mentioned that GTA 6 is indeed still planned for a 2025 release but they're also not ruling out a delay to 2026.