How much will Monster Hunter Rise sell during it's lifetime on all platforms?  

Most Monster Hunter titles have been single platform releases in the past.  On the 3DS, the best selling Monster Hunter games were MH Generations and MH 4 Ultimate, with 4.3m and 4.2m respectively.  Then MH World came along and sold 16.8m units on PS4 + XB1 + PC.
https://www.capcom.co.jp/ir/english/finance/million.html

Monster Hunter Rise releases on Switch today and is expected to release on PC sometime next year.  How much will it sell?  Will it revert back to 3DS like sales or will it sell more like MH World?  Perhaps it will land somewhere in between, or even exceed MH World?  What do you think?

I'm going to guess 5-6.9M. Most of the 3DS releases almost hit the 5M mark, and this will be available on two different platforms. If there is no "ultimate" version, and instead a large expansion for the game I will bump up my prediction to 7-9.9M. Most of the 3DS releases almost hit the 10M mark if you include their ultimate variants, though that also includes those who made duplicate purchases; hence why it isn't doubled.

I'd love to be proven wrong though. There are a lot more Monster Hunter fans now than their were on the 3DS.

A bit less than World I think. My bet is the 10-14 million range 

Seems like the critics consensus is World still the best Monster Hunter 

Im going with 12m-14m.
Its got great reviews, even if it is not as good as World, thats too high a standard all the same. The franchise has fully entered the western market by now and its going strong.
Marketing around the game was really good as well.

I voted over 15 million. I think it'll break 10 million on Switch (5+ million in Japan alone) and I have no idea how much it'll sell on PC but I think between the two there's a good chance it finishes just over 15 million.

I picked the 20-25 million option. I’ve always been more on the positive side when it comes to Switch games sales, yet my predictions all seemed a little too conservative, so I am going all out on this one. learned to never underestimate the Switch.

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.

I voted in the 10m-14.9m category. I think the success of MH World will translate to MH Rise, but Rise is only on two platforms. However, I realize that I may be underestimating sales just based on the "Switch factor". People seem very eager to buy Switch games right now, and that may or may not give another big boost to Rise.

17 million...on Switch alone

I say 10m - 14.9m, including the expansion rebundle that it will get (because people forget that even though Capcom moved away from doing "Ultimate" editions as the only way to get an expansion, they still sell bundles similar to Ultimate, both digital and physically - I.E. Monster Hunter World: Iceborne's Master Edition which includes the base game and the expansion).