I mentioned this in another thread but seriously, I think the reason the Wii U isn't lighting sales charts on fires is because the casuals aren't into it. And really good riddance to bad rubbish I say.
Nintendo still made a profit with the GameCube and even bigger one with the N64. Let the casuals go, they were an unreliable, flakey market that wasn't interested in any serious game experiences outside a little Mario and Mario Kart here and there. That's why with even 100 million users, things like Xenoblade and Sin & Punishment could barely find an audience, and more core IP like Zelda and Metroid really didn't perform all that much better than the N64 or GCN days.
Screw this audience. Now they're all about 99 cent iOS games. That's what gaming is worth to them, so let them leave. They just want disposable, simple, cheap experiences. Nintendo Land isn't hooking with the casuals, Brian Training/Nintendogs/Wii Sports/Wii Fit are old news. Just Dance is the new thing and that'll probably go the way of Guitar Hero in about a year too. These fads come and go.
Who cares if the Wii U only sells around the N64 level (I doubt it would ever go as low as the GCN) and is supported primarily by core Nintendo fans? We got great Nintendo games back then, and third parties don't give a crap about Nintendo either way, so not much difference there. If anything, Nintendo realizing the casual gamer is leaving them may lead to them doing things like actually paying attention to graphics and presentation (read: NEW music) in things like the 2D Mario games and maybe (gasp) trying to make a real breakout hit that isn't some mini-game collection and putting real marketing behind it (like a Monolith RPG).