I'm sure I'm not the only one that has noticed this. But...

Fire Emblem
Poke'mon
Animal Crossing
Luigi's Mansion

Have all either been traditionally handheld titles, or had their last (mainline) major entry on a handheld. In other words they were all 3DS games. 

Will these games all translate well to Switch? Will the developers be able to go from AA development to AAA development smoothly?

What do you guys think? 

They will all do amazing
Fire Emblem 3-5 million
Luigi's Mansion 5-10 million
Animal Crossing 10-15 million
Pokemon 15-20 million

Fire Emblem was originally a console title, and it wont be hard to translate the core mechanics between hardware, so yes.

Pokemon is led by GameFreak which is one of the largest and most profitable devs ever. and already they have 2 projects set to hit the Switch before Pokemon, so they are also fine.

Animal Crossing again, has been on a home console before. and there has been enough Wii U experimentation for them to have what they need to make an HD big budget game.

Luigi's Mansion is a niche spinoff title. The Gamecube game was meant to be a tech showcase, but gained a cult following. The 3DS version was chosen specifically so they could use the 3D aspect, which was originally planned for the Gamecube but scrapped for obvious reasons. LM3 will be the first game without hardware limitations holding it back, after two games and a remake of them pushing the bar as far as they can. i have faith it will turn out great

From what we've seen so far of Fire Emblem Three Houses, it's impressive.
It shows a generational improvement over past installments and the scope of the game is grandiose.
The reason why i mention the game being a generation improvement, is because i honestly think the likes of Lets go P/E would run on 3DS with cutbacks.
Not sure about Animal Crossing or Luigi's Mansion, but what we've seen from FE:TH is something that can make us hopeful for future translations.

I mean I guess it depends on what you define as transitioning smoothly ... as in graphics? Overall presentation? Mechanics? Innovation? Sales? Reception? If we are to consider Let's Go a smooth transition, then yes, all these developers should be fine. Though Intelligent Systems is hopefully making Fire Emblem Three Houses look a little cleaner by now.

My predictions in terms of sales.

Fire Emblem: 5-6M (5-5.5M best guess)
Pokemon: 18-22M (18.0-20M best guess)
Animal Crossing: 17-20M (18-18.5 best guess)
Luigi's Mansion: 7M

What makes you think AC will sell that much? I can see it getting close but 20M?

Out of this games, I'm worried for Fire Emblem and Pokemon. FE because they've been trying to reinvent the wheel since Awakening, and I would love a straight forward FE game, like Awakening was. And Pokemon because Game Freak are both quite lazy and spread too thin as of late.

My predictions:

Fire Emblem: 2-4M

Luigi's Mansios: 7-10M

Animal Crossing: 15-20M

Pokémon: 20M+

So ... they tried to reinvent the wheel ... for one entry?

Sorry, 17-20M is my prediction, not 18-22. Anyways, I simply think it has the highest chances of growth. Though I'm more expecting 18-18.5M