I'm surprised how few people are predicting Skyrim. I acknowledge it's "old", but the game is a perfect pairing for Zelda and has not appeared on a Nintendo console until now. I bet Bethesda(?) is very excited to see how Zelda is flying off the shelves.

ARMS I am not as optimistic about as a lot of people in this thread, but admittedly Nintendo does regularly pull 1 mil with it's game.

I think around 5-6.

Could be some surprises if the install base increases rapidly as it has been. I think FIFA has a shot.

Nintendo should consider a FIFA bundle for Europe.

Pretty much every Nintendo published title has a shot at a million too. 

Dragon Quest XI is a given too. 

Million sellers (WW):

All Nintendo published games basically, Dragon Quest XI, Minecraft, maybe FIFA. 

Over 500k:

Bomberman R, Ultra Street Fighter II, Sonic Mania, Skyrim, etc. 

i say at least 7 million

If it makes out soon, I'd say Project: Octopath Traveller could have a good shot too. Companies that can have Switch product ready for this Christmas are going to cash in. I'm not a fan of the IP, but Take2 really has to be considering a GTAV port. If they could get it out by November, they'd make an easy couple of million in sales. 

I think for sure there will be at least these 7:

Mario Kart 8 Deluxe
The Legend of Zelda: Breath of the Wild
Super Mario Odyssey
Splatoon 2
ARMS
1, 2, Switch
Minecraft

Some games that I think are possible to sell 1 million in the first year are:

SnipperClips
Super Bomberman R
Fire Emblem Warriors
Xenoblade Chronicles 2
The Elder Scrolls V: Skyrim Remastered
Fifa 18
Fast RMX

Sonic Forces and Sonic Mania

But yeah at the very least there should be 7, but I would guess like 9-10 or maybe over 10 considering all the possible stuff that hasn't even been announced for Switch yet. (Such as what may be announced at E3).

At least these 6 are sure bets:

The Legend of Zelda: Breath of the Wild
1-2-Switch
Mario Kart 8 Deluxe
Splatoon 2
Minecraft
Mario Odyssey

Then, depending on their release date, Dragon Quest XI and Skyrim might have a chance and maybe after E3 some more could be added. It doesn't need to be Pokemon, Monster Hunter or Smash, a proper Animal Crossing game should easily set Japan in fire.

Part of me wants to say it won't sell well, but considering the interesting mechanics, the variety of games it's including, and unique games like breath of the wild, it might do pretty good.

At least 5 is guaranteed, unless Odyssey is delayed

Zelda BotW
MK8 Deluxe
Splatoon 2
Odyssey
1,2 Switch

Good chance:

ARMs
Xenoblade

Will have a better estimate after E3

I think all of the following will have a huge chance:

Zelda

Mario Kart

Mario Odyysey 

(shockingly) 1-2 Switch has already shipped 1 million apparently

Splatoon 2

Skyrim 

Minecraft

if Xenoblade 2 launches this fall I think it will have a great chance of doing well, Switch owners will be hungry for a big adventure game

that's 8 that I'm fairly confident will pass a million by next March, most of which will do it at launch

then there's a massive chance (but obvs uncertain) that the following games come close:

Arms

Fifa (2017? whatever EA was referring to)

then possibilites:

Bomberman (shocked to say this but I in no way expected it to be at over 500k this quickly, might have more appeal than I realized)

so I honestly think there's a fairly decent chance that the Switch has like 10+ 1 million sellers have only a year. Pretty remarkable considering it will only have had one holiday season then... but quite possible. I think Mario Kart, Zelda, Odyssey, SKyrim, SPlatoon are all shoe ins. I think Fifa (particuarly because of PAL/Europe), Minecraft, Arms, and Xenoblade may all do great as well.

all it really would take is a few surprise popular third party announcements at E3 that come out in the fall and they're there at over 10 one million sellers. Bear in mind if someone like Capcom announces a Monster Hunter or Yokai watch like game, that's a guranteed million seller. Or even hypothetically if Nintendo randomly has a SMash port for the fall or some obscure Pokemon game. I think there are just a lot of possibilites to get a few more million sellers. The Switch fanbase so far has been seemingly buying a lot of the games that come out, with Snipperclippers and Bomberman having surprisingly great sales 

Some good points out here on "what new games are not yet announced?"  The system is selling great, the right Christmastime ports would likely sell million+:

- GTA V, as others have said
- Dark Souls (unlikely, but like Skyrim, would fit in great with BOW)
- Any Final Fantasy mainline game (XV or VII remake)
- possibly classic 80s/90s sequels/remakes like Bomberman - Mega Man, Castlevania, Resident Evil.

Not that I'm saying we will see any of these games announced, but is it more likley that Switch sells great for 8 weeks and nobody announces any interesting new games for it at E3?