I think Splatoon was rushed out in order to keep software momentum going.
January - Captain Toad (Europe only)
February- Kirby's Rainbow Curse
March - Mario Party 10, Mario vs. DK
April - Mario Kart 8 DLC, Smash Bros DLC
May - Splatoon
June - Smash Bros DLC, Yoshi's Wooly World (Europe only)
July - Art Academy, Spatoon DLC
August - Splatoon DLC
September - Mario Maker
Fall - Yoshi's Wooly World
TBD - Star Fox, Devil's Third, Xenoblade X, Fatal Frame
Winter - Fire Emblem X SMT ( Japan only)
Unannounced software - some of which will be out before April 2016 according to Iwata