Splatoon's biggest hurdle would be whether or not the NX handheld can act like a Wii U Gamepad, or if there is any compatibility with the NX and the Wii U Gamepad (regardless if there is BC or w/e). Splatoon being purely a twin-stick shooter loses a lot of appeal.
I imagine they'd just put a gyroscope in the controller and then make you use a select menu for the map.