I think capcom knows the move to modern consoles won't happen overnight. MHW sales might take a bit of a hit at first but they can build it back up overtime. The future of the franchise is bigger than one game.
They can't stay on 3DS forever -- the fact that the best selling game is on PSP suggests to me that the game's sales were actually held back by staying on weak hardware. It's been like 10 years and the game looks and feels mostly the same. It felt to me like the series had stagnated -- sure, there's been refinements, but look at what other games have done in a decade and MH looks kind of silly. All this plus the fact that handheld gaming has changed since the PSP days suggests to me that moving to modern consoles could very well be a great move in the long run. Larger global install base will help a lot, longtime fans that weren't impressed with the 3DS games will have a reason to jump back in, and a fresh new monster hunter is a great opportunity to pick up new fans. Exciting times.
And I'm sure some of the backlash is from purists that can't imagine playing monster hunter with updated mechanics, but it also definitely feels like console wars play a big part. There's a lot of assumptions about the series' sales being safer on Switch -- somehow moving to PS4/PC/XBO is some huge gamble but moving to Switch isn't? Uhhh, what? And for some reason, a lot of people think the series was niche on PSP and 3DS made it into the success it is today, but it actually sold best on PSP. Then they changed it to "in the west" but mhgen us/eu sales aren't better than mhfu's so it's not like there's a clear growth (4U did see a bump but they didn't stick around). In fact, Tri on wii sold better in the west than every game except 4U, suggesting home consoles might be the place to be in the west. It might be risky for Japanese sales, but again, they can't stay on 3DS forever so I'm not sure they had an option there. At least in the long run, PS4/PC/XBO definitely feels safer to me than sticking on 3DS much longer or moving exclusively to Switch. If it's not console fanboyism, maybe it's just lazy thinking (portable = super sales, console = bomba).