It seems that due to some type of error, all cars are available in Forza Horizon 4 thanks to the fact that some users of Windows 10 have been able to pre-download part of the game (90GB) and among the files we have the complete list of cars which is around 500.
https://www.youtube.com/watch?v=VmQNo8xtcAg
Forza Horizon 4 is expected to be launched in October 2018 as part of Microsoft y Playground games and these are the cars that will include.
Complete list of cars in Forza Horizon 4
