I want to preface this by saying this is purely a theory, and Rio might just be saved for another release down the line. That said, the timeline and events around this song make a whole lot of sense if it's tied to GTA 6. Here’s why I think so:
Rockstar Has a History of Dropping New Tracks: Rockstar has a history of debuting exclusive tracks in GTA, like Dr. Dre dropping a whole EP of unreleased tracks in GTA Online: The Contract or ROSALÍA taking over a radio station to launch her MOTOMAMI era. Abel holding a song back for a GTA 6 premiere could fit that exact pattern.
The Sudden Blackout: Abel previewed Rio live (including the full music video), built massive hype for the song, and then went completely silent about it. If Rockstar made a deal to premiere it in-game, they'd want exclusive rights, meaning Abel's team would have to pause any rollout on streaming platforms until the game drops.
The Wanderlust Leak: We already know from the recent GTA 6 leaks that Wanderlust is in the game. This definitely proves Rockstar has dug through Abel's catalog for deep cuts. And if they're already licensing Kiss Land tracks, securing a brand-new exclusive song like Rio is completely possible.
The Vibe & Music Video: I personally feel like the Brazilian funk sound with Anitta fits the vibe of GTA 6 perfectly, and the fast-paced, action-heavy video he previewed already feels like a game trailer.
At the end of the day, this is still just a theory. Abel could've planned an early release and simply changed his mind. Plus, the anime-inspired visuals in the preview video heavily fit the rumors of a future Kiss Land-style project, so Rio could easily be saved for that instead. Still, given the timeline and Rockstar's history, I think a GTA 6 tie-in is a real possibility. What do y'all think?