As many as they can get, really.
1st Quarter: BOTW, MK8D
2nd Quarter: Splatoon 2, Mario and Rabbids, ARMS
3rd Quarter: Mario Odyssey, Xenoblade 2, Fire Emblem Warriors (and a bunch of third party ports ala Rocket League, Skyrim, DOOM...)
4th Quarter: ????
(Mario Odyssey and BOTW heavily carrying it, here).
So, it's pretty much as many as they can get. If we skip ahead to 2018, to maintain popularity they need to announce a new game for a 2018 release date that is on the verge of BOTW/Odyssey popularity, if not miscellaneously Kirby, Yoshi, Fire Emblem, No More Heroes, etc. A good E3 could definitely do justice, but I;m convinced that this year will be better for first-party Switch games than the next. Next year, hopefully, it will be carried by third-party developers. The next "big" first party title in terms of maintaining popularity is definitely Pokemon. It's probably 2019 though.
