Splatoon is probably screwed.
To get that game out there, Nintendo would need to advertise it heavy and hit with a entertaining theme or push for it that appeals to all ages.
They tried that with the new Smash Bros games and the tag line "Settle it with Smash". I doubt they are going to give Splatoon as much of a push based on how they do most of their non-major franchise titles. Tragic but they did similar failings with Pikmin 3 and Wonderful 101 in 2013.