They might release this in 2021, but dont expect a whole lot of cars and tracks. The situation might be similiar with Forza 5, which was a generational leap as well. The biggest difference today is that we wont see a Forza 9 two years further down the line. Judging the recent strategy shift with Halo and Gamepass, i expect that this will be the only Forza Motorsport for Series X, a game that will evolve over time just like Halo Infinite. It makes sense because of the Gamepass focus, MS will most likely earn more Cash with Gamepass subs and DLCs then with traditional sequels which come out every two years. This makes a launch with limited content even more likely. You dont have to complain, because you dont have to buy the game anyways, its all on Gamepass.