Zelda and Smash Bros are certainly not enough to sell the Wii U, but you're flat out wrong if you think Mario Kart won't help its sales. Sure, Gamecube and N64 had it too, but, at that point, MK's popularity was at SSB's level, but, at this point, Mario Kart, with in the ballpark of 40 million games sold this generation alone, is one of the most popular gaming IPs in history. It also helped sell the Wii, for the record, since it helped the DS audience approach the Wii and will most likely do the same for the 3DS and Wii U, but in a far higher amount since the brand popularity has increased several times over with the Wii. On top of that, it has another immense 40m+ this generation brand that it didn't have with the GC and N64; it's called Super Mario Bros.
Also, while it's true that the Wii was the largest, most unlikely coincidence ever, since motion exploded and MS and Sony made fools of themselves at the same time, Wii U doesn't need to be. They had nothing but an unreliable and miniscule base back then, yet now Nintendo is probably one of the most accepted family entertainment brands ever and their audience is probably impatiently awaiting the next console.
Your next paragraphs are just opinion so I won't bother, but I find it difficult to believe that the userbase that bought well over hundred million Mario games this generation and the same for the Wii series will let a console with Wii in its name sell less than 60 million. Your hypothesis of N64-esque sales seems downright amusing.
“These are my principles; if you don’t like them, I have others.” – Groucho Marx
