On a personal anectodal note, Nintendo has big problems.
First of all marketing. Sounds silly, but even if it might not even lead to sales, they need to at least make people aware off the product and get some chatter going. For crying out load pretty much all the people I know who are remotely interested in gaming know about the PS4, but not the Wii U despite it being out for months. I mean when I visited my cousin's in London, I only saw a couple adds. But on the way back in Sheffield, Manchester and home in Newcastle? Zilch.
And then there's the audience itself. Between my friends and family not one person is interesed in Wii U. I am the sole exception. The so called hardcore group feel burned by the Wii, and have distanced themselves from it. My brother told me I was silly for wanting to get one. The 'casual' group have long since packed their Wii's away. When talking to them about it, they say it was fun for a little while then they got bored of it.
And then software. There simply isn't enough quality exclusive games on it. Of the people I know, only I am wanting to get a Wii U, but for someone who doesn't like Mario, why should I get it now? When Zelda and X come out, it'll be a different story, but for now there's not enough worthwhile games