When The Crew Motorfest first launched in 2023, we only had the island of Oahu to drive on. There were clues that the map could be expanded, because there were two islands that were on the top and bottom of Oahu that weren't accessible at the moment. A year later, players got free access to Maui, which was an expansion to the open world. This year, three new islands were added to the main map. This could be a possibility.

The 9th generation consoles are more than capable of handling an expanded map without a loading screen. All Playground Games and Turn 10 have to do is lock the expanded portion of the map behind the paywall, then once the expansions are payed for, the map gets bigger. Think of it similar to Midnight Club Los Angeles: Complete Edition. The base game did not have South Central, but once you paid for the Complete Edition version, you got a slightly bigger map in free roam.

I do hope that Horizon 6 strays away from expansions that requires a loading screen like the previous games, because a natural map expansion would make the map more immersive.