I think it is too early to be able to tell.
I think a lot of "core" fans(and that includes gamewebsites and their staff)have an unfair bias against Nintendo. I think it boils down to identifying with the games people play, and then feeling threatened by Nintendo because they don't promote the same types of gaming experiences. Because of that Bias, I think a lot of "stories" and critics are floating around predicting Nintendo doom.
But if you think back to Wii, the same type of things happened. Hell, people have been predicting Nintendos fall for a couple of generations now.
If your asking if Nintendo will compete with the Sony and MS systems, if Ninetdno will out "Microsoft" them, if Nintendo is going to be the new home for OMP shooter fans, if Nintendo will champion the core...then the answer is likly no. But they didn't do any of those things with Wii, and they thrived.
Many folks have the misconception that PS360 style systems and game offerings are the only things that people want to own or play. That is just plan wrong. Infact, if MS/Sony release the same franchises on new hardware at expensive price points, they may actualy contribute to increased WiiU sales.
I think there will always be a market for Nintendo and their games.
But, as for the WiiU selling tons of units and matching the Wii...I think that will be hard to do. I think it really comes down to price point. If the system is 149usd to 199usd it will move fast off of shelves and be hard to keep in stock. If the system is priced above 299usd it will be hard to move.
And before you condem Nintendo on price alone, think about how much the new systems from MS and Sony will cost? I don't care how good those systems are, if they are priced 600usd and up, they won't sell either.
I think it all hinges on price point. For all of the up and coming new systems. Games too, they better start all bringing new and fun games, but if the prices are too high none of them will sell.
So best to take a sit and wait to see aproach. Time will tell all.