It's certainly no full step up in magnitude from the Xbone, and it doesn't have any new input/output capabilities, or any new games.
That said, the Switch isn't really a big step up in power from Wii U either, but it could be labeled next gen in the sense that it indeed is Nintendo's new flagship console.
So I think it could really go either way. I wouldn't be against counting it as part of the 9th gen.