I'm torn. I personally don't think any of the next gen consoles will fly off the shelves in their first year, but I do believe they will sell through a heck of a lot more than the Wii U has, but the proof will only be seen when it happens. Until then, it's just a shit load of (daily) speculation. Man, we've got another year of this haven't we!
With regards to the Wii U utterly failing - I'm not sure. I still think Nintendo can turn this around, and a slew of first party titles around Christmas should see a bit of an upward trend. They will always be the "other console" but they seriously do need to market it a lot better because through my own anecdotal evidence nobody seems to know what the hell it is.