Currently, the following games are either announced or confirmed:

Announced:
Dragon Quest X
Dragon Quest XI
Just Dance 2017
The Legend of Zelda: Breath of the Wild
Project Sonic 2017
RISE: Race the Future
Riverside
Tank It

Confirmed:
Unknown Pokémon game
Unknown game by Image & Form

Other:
A new Super Mario Bros. game
The Elder Scrolls V: Skyrim — Special Edition
Mario Kart 8 (sequel or updated release or DLC; too little information available)
NBA 2K17
Splatoon (sequel or updated release or DLC; too little information available)

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So, the Nintendo Switch is the first cartridge-based home console since the Nintendo 64.

And apparently acts as a "third pillar", not replacing the Wii U Wii U Wii U-- sorry. Not replacing the Wii U or the 3DS.