Zelda isn't the sales driver people like to pretend it is. It's about the most hard core game Nintendo has and has a very strong, devoted following, but it's really not their strongest franchise. They need a Mario before Christmas period.
If they really want to come out swinging they need a damn good Mario game day one. Mario sells consoles, especially when done how the fans want and 3D World is a game many wanted and enjoyed but it came later than the game people weren't asking for. THIS is a game we have all been asking for since the last Galaxy, even people that actively hate or dislike Wii remote still bought and loved Galaxies.
Mario Kart and Splatoon in the same holiday makes it a good showcase for the console and gets a broad variety out up front, a competitive shooting game, a competitive racing game, an open world RPG-like game, and a Mario game that looks like it should be fun.
Having too many games up front is not a bad thing either. Getting as many of the sequels and franchise games out of the way as they can up front gives them plenty of room down the road to experiment. They need to space out their side stuff like DK, Kirby, Metroid, F-Zero, Punch Out, Excite Bike, etc, but they are going to want to get as many games as they can as fast as they can.
I also bet they have something Pokemon related ready by the first holiday.