I think Switch will get a few 10m+ sellers from third parties, and the best way I can describe it is to talk about the NES by analogy.  Here are the top 10 NES first party games (excluding SMB and Duck Hunt)

1. Super Mario 3 (18m)
2. Super Mario 2 (7.5m)
3. The Legend of Zelda (6.5m)
4. Dr Mario (4.9m)
5. Zelda 2 (4.4m)
6. Excitebike (4.2m)
7. Golf (4m)
8. Kung Fu (3.5m)
9. Baseball (3.2m)
10. Punch Out!! (3m)

At the same time, here were the third party games that sold a comparable 3m+:

1. Tetris* (5.6m)
2. Teenage Mutant Ninja Turtles (4m)
3. Dragon Quest 3 (3.9m)
4. Dragon Quest 4 (3.2m)
5. Stadium Events (3.1m)

It's true that no third party game got anywhere close to the sales of the Mario games.  However, the top NES third party games were around the same level as the rest of the top NES first party games.  It's definitely possible for third party games to be very successful on a Nintendo system.  And sales of 3m+ on the NES is fairly analogous to sales of 10m+ today.  (Factor in population growth + NES mostly had a presence in only US and Japan + Switch includes home and handheld markets.)

All of those third party games were from franchises that started on the NES.  So, I think Switch will get some third party hits too.  Every generation has a new set of third party games that become fairly big.



*I'll let you decide if you want to count Tetris as first or third party.  It was technically created and published by Nintendo, but really it was first created by a Russian man and the game is owned by the Russian government.  Nintendo put more effort into securing the licence than they did into actually making the game.  Either way there 4-5 third party games that sold like first party games.

3 already confirmed, so far.
Then, there's Smash, Splatoon 2 might really get there in a couple of years.
Let's Go, too.

Tto be released games:
Pokémon 2019, 2020, 2021
Animal Crossing

In total, 10.
11, for the surprise title either Mario or Mario Kart related.

very interesting, I do believe a new DQ game could do really well on switch...

btw pokemon at 4M for 24th november week, I guess with the nintendo upgrade of 31th December it will be around 6-7M ?

Already done it:
SMO
MK8:D
Z:BotW

Will hit next year (or games that come out next year that will hit it):
Smash
Pokemon Let's Go
Pokemon
Animal Crossing

Might trickle it's way there:
Splatoon

Darkhorse:
NSMBU

Future:
At least 1 more pokemon game
Probably another Mario (2D or 3D)

That's 11 and I see that being the minimum (or 10 if Splatoon doesn't quite reach it). Who knows maybe Switch will actually get some major AAA games in the future and we'll see a third party 10 million seller.
Basically, almost guaranteed to have 10-15 games.

So I updated this thread!! we got two new 10 million sellers, and splatoon coming closer. Also, SMP with an impressive debut, do you think it will reach the 10 m? which is gonna be the next title to reach it?. Looks like I underestimated the power of pkmn btw...

These numbers are insane. Even Let's Go is outpacing ORAS in the same period despite costing 50% more and being on a smaller install base. Breath of the Wild is over 13 million copies if you add the Wii U version, making it the best-selling Zelda game by over 40% on the second one (TP) already. Super Mario Odyssey is already the best-selling 3D Mario.

It will be tough! So far there are no signs of supporting the game with free updates....... 

Splatoon, Mario party, nsmbud, animal crossing and Pokemon gen 8 all have a chance at 10 million. Bringing the total to 10. We'll probably get another Pokemon game over 10 million after gen 8, Minecraft might make it, that brings it to 12. Plus we might get another surprise or 2.

not really sure about nsmbud but it might have long legs so yea maybe

Well the only nsmb game that failed to sell 10 million was on Wii u. I think with the massive success of Mario kart 8 on the switch that nsmbu has a chance at dragging itself over the 10 million mark.