Let's not forget that if we combine sales of original and Ultimate versions then MH4 and MH Generations both topped 8 million so those games also sold extremely well (As a side note I think its more likely that Rise will follow in Worlds footsteps and get an expansion and a "Master Edition" including that expansion than for them to go back to the "Ultimate" thing, but some sort of reversion later on seems like a given with this series).
I voted for 15-20 mil, I don't think it will top World in total, but I think it will be do better in Japan while still being very succesful in the West as well.
- Switch - 27m
- PS5 - 15.5m
- Xbox Series - 10m