They should bury the Wii U and just admit that they fucked up. Fans will understand.
Tell it to Sega. Cheapest launch price ever, most launch sales ever, an utterly absurd attach rate for both software and hardware, and the DC still failed after two years of "remember the Saturn?" It becomes impossible to keep a system alive when nobody wants to publish a damn thing, because they don't think any of it will sell, and what does get published is barely stocked and advertised, so getting it into hands is next-to-impossible. All it takes to set that in motion is perception. Or even the
perception of perception (like, whoa, man.)
Nintendo's survived a serious hardware flop once before, with nary a scratch, but it was only an over-ambitious side-project... not one that superseded their moneymaker. By contrast, the GC made them money until the bitter end, because they supported the hell out of it, and kept their base from wandering off
too far. If they junk the WiiU too soon, it will be nothing but a middle finger to those who bought it despite its problems, simply because it would be the home for core Nintendo games for half a decade.
Sega did this with a less hyperfocused library of "big" titles, and had their arcade roots to point to as necessitating better hardware. Nintendo would simply be breaking an implied promise to their loyalists, who they need the support of once again.