2019 has not seen (and will not see) the release of any game of the Forza series but this does not mean that the franchise has been abandoned. While Turn10 is working on Forza Motorsport 8, Playground Games seems to have already set up Forza Horizon 5.
The English team recently welcomed the Forza team to Nathan Buchanan, who arrives at the Playground Games and Microsoft court after spending many years in the British studios of Rockstar Games. The firm has never directly cited Forza Horizon 5 speaking generically about Nathan’s entry into the team “working on the future of the Forza series “, explicit references to the upcoming Forza Horizon 4 expansions and the next chapter of the saga.
2020 will in all probability be the year of Forza Motorsport 8 (destined, it is rumored, to accompany the launch of the Xbox Scarlett on the market ) while Forza Horizon 5 should see the light in 2021, it is still too early therefore to learn more.
Playground Games is also working on an Open-World RPG repeatedly associated with the Fable series (Fable IV or a reboot?) But at the moment nothing has been confirmed and even in this case, it is only speculations awaiting official status.