According to a new rumor, GTA 6 technically has more than one map. Extensive reporting, numerous leaks, and even some potential teasing from Rockstar Games itself here and there, all point towards Vice City, the series' fictional take on Miami, as being the game's primary setting. The emphasis here is on "primary," because the expectation is there may be more of Flordia as Rockstar Games fleshes out the area surrounding Vice City/Miami.
At various points, courtesy of various rumors and leaks, we've heard that part of the game's map will be The Caribbean. The latest rumblings of this come the way of Matheusvictorbr, a well-known leaker in the GTA community, and a leaker who leaked that the game has two protagonists and that one of these two characters is female. According to the insider, the Caribbean islands are in the game, but will not be included in the open world itself, which suggests that at some point in the game players will find themselves in the Caribbean, similar to how a whole chapter in Red Dead Redemption 2 takes place in Guarma.
That said, while Rockstar Games used a secondary map with Red Dead Redemption 2, it hasn't really done this much with Grand Theft Auto. Further, the Caribbean is right next to Miami, so it would be odd for there to be a separate Caribbean map when you could just tack that onto the main map.
All of that said, take everything here with a grain of salt. While the source in question has been on the mark in the past, they've also been off the mark in the past. Further, even if everything here is accurate, it doesn't mean it will remain so. Rockstar Games has a reputation for cutting lots of content towards the end of development, more so than other developers, and not because it's unfinished but because it's deemed insufficient. It's believed hours and hours of Red Dead Redemption 2 were cut pretty close to the end of development.
As for Rockstar Games, it's not commented on this new rumor, and considering it hasn't commented on any previous rumors, including ones for much more prominent sources, we don't expect this to change. However, if expectations are bucked, we will be sure to update the story accordingly.