In an interview with Waypoint, Reggie makes it sound like Prime 4 is shipping in 2018.
Reggie Fils-Aimé: The response to what we’ve showcased, and it really is just a small tip for 2018, has been exceptionally positive. You’ve got fans seeing Metroid Prime 4, hearing that Mr. Tanabe, who’s been involved in all of the Metroid Prime games, is going to be at the helm of that, the fans are tremendously excited. To hear that there’s going to be a core Pokémon RPG experience on the Nintendo Switch, the fans are incredibly excited. To see a traditional Kirby experience, with him inhaling enemies and copying abilities, fans are excited about that. And then the Yoshi game that we showcased, with that unique, you know, motion to go “behind-the-scenes,” so to speak, has people really intrigued. So just by showcasing those four games, and giving a little bit of a taste, yeah there’s a lot of excitement to what 2018 can hold.