Do you not remember last year? If they hadn't purposely delayed Donkey Kong, Mario Kart 8 would have been the lone retail release for the entire first half of the year.
You're forgetting Wii Fit U's retail release was in Feb. Then again everyone forgot about that game...
I'm sorry, but this is ridiculous logic. Not every Wii U owner has a 3DS, and not every 3DS owner has a Wii U. Your vehement defense of the corporation is truly baffling. That being said, I expect to see the Smash 4 DLC in April. I'm surprised a Direct hasn't been announced yet.
Nintendo taking turns with 3DS and Wii U promotion is probably a good thing. They truly do cannibalize each other.
Just look at holidays 2013, when they tried promoting the 2DS w/ Pokemon, then the Wii U with Mario 3D World + Zelda: Link Between Worlds a month later. While software sales were eventually fine, both pieces of hardware did way below expectations since they kept switching b/w the two (2DS/3DS had a great launch in Oct and then suffered through Nov/Dec, and Wii U only picked up in December that year).
They can and should space out the games so they can space out the marketing since Nintendo clearly doesn't seem to be able to do both.
Thus 2015
Jan - Kirby should have been put here imo (like in JP), but Smash, MK8 & Toad generally carried things along
February - New 3DS XL + Majora + Monster Hunter all did really well and were marketed quite a bit, Kirby Rainbow Curse did not do well
March - Nintendo markets the Wii U w/ Mario Party 10, Codename Steam looks like it's going to sell badly
They're competing with themselves and I don't get it when there are free months open. Codename Steam could have released in April w/ Xeno so that they could market it the 3DS again.