At least three. These are the titles I classify as 'major exclusives' that are guaranteed to come to Nintendo platforms --

3D Mario
2D Mario
3D Zelda
Smash Bros
Mario Kart
Splatoon
Pokemon
Animal Crossing

Games like Metroid Prime 4, Fire Emblem, Xenoblade or whatever Retro, Platinum, From Software and others are working on can also qualify as major titles as long as Nintendo positions them as such -- kind of like how Star Fox Zero was pushed as a major exclusive even though the series never reached the same levels of success or influence as Nintendo's traditional system seller titles. Once Pokemon starts doing its yearly release thing, I still think the Switch should have three other 'major exclusives' to go with it.

I think 2-3 major exclusives are enough. They are selling a little less than the PS4 with Splatoon 2, Mario and Zelda as major titles. Didn't they already announced a new Metroid and a major Pokemon game releasing in the near future ?

We should get at least 2 Metroid Primes, 2 Marios, 2 Zelda's, 2 Splatoons, 1 SSB and 2 Mario Karts before the 5-6 year cycle is up. Given that we've seen 1 Mario, Zelda, Splatoon and Mario Kart launch in 2017, if done right, they could stagger the next title out each year over 4 years. If you add in Metroid Prime and Smash, it gets even better.

Sprinkle in the B games like Kirby, Animal Crossing and Xenoblade etc... they should be alright.

You think Animal Crossing is a B game?! I invite you to take a look at how much Animal Crossing has sold on DS and 3DS.

Spoiler alert: Animal Crossing is easily part of Nintendo's top five biggest franchises.

Not that much but 1 big and 2-3 smaller games would be amazing.
Also 1 new ip each year

I love Animal Crossing and I've played it since 2002. But I was refering to the console versions, not handheld ones.

Well, the beauty of Switch is that it'll get the best version of every franchise. It's not like the 10+ million people who bought Animal Crossing on 3DS will disappear. Animal Crossing on Switch will be just as big as the previous handheld versions because there's no alternative.

You don't think there will be an impact due to the higher cost of entry? 

That will depend on how well the market reacts to the Switch's current lineup but so far the Switch will need at the very minimum of 2 flagships (games that will go on to sell 5M+ units in their LT) per year to maintain current demand ...

With Nintendo depleting their potential rather quickly (they already used Zelda, 3D Mario, Splatoon and not to the fullest extent Mario Kart) that leaves them with Pokemon, 2D Mario, Animal Crossing, Smash Bros and those with potential to become flagships includes Tomodachi, Luigi's Mansion along with Donkey Kong ... (Nintendo will have released 4 out of their 11 biggest current franchises for Switch in it's first year!)

With Monster Hunter and Yokai Watch not being as strong as they were, Nintendo will find themselves at an impasse with the Switch once they used all of their biggest franchises ...

Even using 3 of their biggest franchises a year still gives Nintendo over 3 years before they run out of their top IP's. Also, Mario Party has the potential to be a 5+m franchise on a successful console, as does Metroid if Nintendo can create enough hype for it. After 3 years Nintendo can begin to offer sequels to the aforementioned big hitters. Also, there are collaborations, unknowns and new IP's to think of. 

If anyone has the IP's to pull it off, Nintendo has.