Reason 3 is incredibly odd. I don't know why Prime 4 coming to Switch would make them want Dread to suck. And while Dread was great it didn't seem like it would be exceptionally resource intensive. It's a modest lengthed 2D game, and it's not huge even by 2D standards. Again, it was great, but not a huge commitment.
For reason number 2, again, Metroid Dread. I believe Mercury Steam starting on it shortly after Samus Returns, but we see anything till at least 3 years into development. The only difference here is that Nintendo jumped the gun and announced Metroid Prime 4 kind of early. But, it's not uncommon for them to work on a game 3 years without releasing anything.
As for reason number one, that's iffy at best. Sometimes Nintendo's studios do that. The division that made Mario Galaxy only worked on sort of minor projects and remakes from Galaxy to I think Odyssey. So, it's not unheard of. I don't know enough to really determine what the hiring stuff means. As the plan was for Namco to do Prime 4, then that would have thrown a wrench into anything else Retro would have been doing, and would somewhat explain a lack of output.
I'm not saying it will definitely come out in the near future or on the Switch, but I don't find your reasons for believing otherwise convincing.







