Based on Iwata's comments I have the weird idea that Nintendo is essentially going to release DKC and some minor titles in February (Wii Fit U retail, Lego Movie) and then sit until May w/ Mario Kart. The thing he said after "we will ensure that momentum will continue after Mario Kart".
My guess is Nintendo couldn't sustain momentum from now until May, so they're going to sit March (and possibly April) out, and then start in earnest w/ Mario Kart in May. I can't say I like the decision and have no idea whether it'll pay off.
If Watch Dogs is a May/June release and stays on Wii U, Nintendo may have Mario Kart & Watch Dogs release close to each other, and hope the sales from Mario Kart lead to some sales of Watch Dogs as well. If Nintendo then started releasing the other titles on their 2013 lineup (Zelda Musou, X, and Smash for example), they might be able to pull in some momentum going into the 2014 holidays with Smash being the likely holiday title. This is just going on announced titles, and I'm hopeful Nintendo has something under wraps, like a new Animal Crossing or that NFC title they keep hinting at. I do honestly think a console Pokemon spin-off with a good bit of effort put into it could sell well on Wii U (considering how popular the main Pokemon series clearly still is w/ 11m+ shipped in 3 months).