Coming from a GameSpot interview with Tekken producer Katsuhiro Harada...
GS: So, no Nintendo Switch version (of Tekken 7) to reveal?
KH: We're quite surprised by the Nintendo Switch announcement; read into that what you like.
Bandai Namco and Nintendo have an absolutely great relationship right now. There was even a Tekken game at Wii U launch. At this point, I'd be surprised if something special wasn't in the works.