This isn’t the first time Forza and Hot Wheels have teamed up. The second expansion pack for Forza Horizon 3 was also Hot Wheels themed, and took players to a separate open world area made out of stunt track pieces.
Forza Horizon 5 has an Expansion Bundle available on the Xbox Store, which “includes two game expansions when they become available. Each expansion will introduce a new location, vehicles and gameplay.”
Fortune Island saw players travel to a mountainous island filled with tough terrain. The expansion features the single largest mountain road in the history of the Horizon series. It also added 10 cars, which could be used in the main game.
Lego Speed Champions added the Lego Valley, a new location in the game in which most of the environment was made of Lego. This expansion added five Lego versions of popular cars, several of them based on real Lego sets.
source: Video Games Chronicle