Snowmobiling blues...

I think Yamaha is still making a fan-cooled twin two stroke according to the 2019 buyer's guide. Yamaha has teamed up with Arctic Cat and they have there 4-stroke Genesis motor that they're trading back and forth and putting a turbo on and it does very well in the Deep powder it's just so powerful.
You are right, Yamaha is selling a 2 stroke 540cc since 2017.

BTW, looking today for a new snowmobile. Winter is not far away.