Well it will at least pass 10 million in total, though looks like it won't pass 10 million on Switch alone as I had figured. Though it should get close on Switch, with the expansion coming this year plus likely price discounts in the future.
But Capcom now has a great thing going where they have an extremely popular World series on Playstation and a very popular Rise series on Nintendo. Makes sense to keep each one separate so they can each be made well specifically for the two respective systems going into the future of the MH ip. MH in japan of course has way more competition on Nintendo systems than it does on PS systems because most large franchises in Japan are on Nintendo, and it feels like World is more AAA than Rise too, which no doubt accounts for some of the sales difference. But MH is now a very strong franchise with two separate series that sell very well on both Playstation and Nintendo, which is great for MH and gamers alike.
Nintendo finally got Dragon Quest back (albeit very late), still missing Final Fantasy, and now has a main MH series as well. Those were the three huge Japanese franchises Nintendo consoles had been missing out on for a long time. If anything, MH and DQ should become even bigger franchises on Nintendo in the future as the Nintendo fanbase starts getting used to these serie and these companies see that these games are worth a lot of effort and very profitable on Nintendo. Good times for Nintendo gamers!