Coming in Summer 2017.
http://www.nintendoworldreport.com/news/43937/splatoon-2-coming-to-switch
Splatoon 2 will be coming to Nintendo Switch in Summer 2017.
The game will include new items and weapons, including an artillery-style weapons and ink jetpacks. Players can use the Joy-Con or the Pro Controller, and it can be played on TV or in handheld mode. Gyro aiming controls will be an option in both modes. You can play online or against others in the same room.
I'm surprised they didn't call it Spla2oon.