I'm really, really excited for Splatoon! I got to try it in the recent "Global Testfire", which I think was more a server stress test than a proper demo, but for the hour that I got to play, I had a lot of fun. I want it even more, now! I haven't been this excited for a game in ages. Something about the art style and the theme just kinda grabs me.

That said, I have to agree that it probably won't be a system seller. The introduction of a competitive shooter might broaden the demographic a little and attract more buyers, if that particular demographic wasn't already plenty happy with what the other current platforms have to offer in the same genre.

Personally, I still haven't picked up either the PS4 or the XBox One. I could afford to, but there hasn't been a title out yet that really sells either console for me. I'm pretty happy with what the Wii U has to offer, so far.
If the NX is really Nintendo's plan to phase out the Wii U soon, though, that kinda bums me out. It's been just a few years since the console came out. That's less time than what separated the GameCube and the Wii.