Already said it in a previous post, and I won't do quotes because there'd be too many in one post, but...
- Why do some people think that Capcom working on one would mean they're not working on a next-gen one? That's not how game development works for big companies, and not how Capcom has ever worked for MH (or even for RE if you want to use the argument that the games weren't as big before, even though MH4U has 682 people in its credits and Gen had 650).
- The argument that they wouldn't do that because it'd cause lower sales doesn't make sense when it'd still sell more than most of their games and would be less expensive than World to make. Capcom, like many other companies, also search for more revenue sources, not less.
You can bet that World 2 will sell less than World 1, that doesn't mean they won't make it. They'll change their pipeline and design for better profit and more sequels/expansions/spinoffs/dlc.
- The argument that a Switch exclusive would be a mistake is kinda linked to that, even though nobody really says that it should be exclusive. Capcom has shown this gen that they have different expectations in terms of userbase depending on the platform, even if X game would run perfectly well on more platforms. On top of that, there's design and marketing issues that could lower the image of this game (graphics, scope, etc). But again, no, there's no-one saying it should be an exclusive.
- The "it won't run on Switch!" argument doesn't make sense if the game is made from the ground-up for Switch (be it on MT Framework that they still use, on UE4, or something else like a "mini" version of RE Engine like when they've made one for MT Framework in the past for similar purposes). World is an unoptimized mess, and the idea of a port left a long time ago. That's not what people are asking for.
- Again, no, most of the team members of the MH Division don't work on a single game. Or hell, Capcom as a whole. Compare game credits at Capcom to get an idea.
The MH4 leads were on World and now on World 2. The GU leads have been on Iceborne. The Generation/Portable leads haven't been on something in a good while.
The only valid argument is that Capcom's Switch support is pretty underwhelming (to be polite) and that it's hard to see them do that because that'd mean they actually care about the platform. Then again, we've seen bigger reversals than that in terms of support, even recently (like Atlus porting Catherine to Switch with a lot of care, 2K's support, EA slowly coming back, etc).
Do the old rumors about MH Switch make sense? Yes. Is it fine to think it won't happen? Sure.
But it's ridiculous to think it won't happen while talking about the 5 "arguments" above.