I think it is just very easy just to blame "Wii U owners". I've already said this before, but if this game fail it wont be only Wii U owner's fault, it is every gamer's fault. I'm not expecting people to have spare money to buy a console to play TW101, but if it is a problem it is a problem with gaming in general, and not only exclusive to Wii U owners.
The game is amazing and is everything people complaining about the industry stagnating in a few genres and titles that are basically all the same keep on saying games should be. It is a new IP, it has its own style, it has challenge and minimal hand holding, it has a deep combat system and tons of unlockables. Has a long main single player that is filled with Easter eggs for the gamers, and it can be replayed over and over again. But still people will just ignore it and buy the same old games again. We have seen this happen before. We've seen Okami be completely ignored on the PS2 even with its ridiculous install base. We've seen Bayonetta struggling to sell 1.3 million across two successful platforms. And this is only to mention two other games made by Kamiya.
For a fan of the genre it is really sad to me. Gives me a felling this type of games will either be westernised to appeal to a greater audience or maybe will cease to exist completely or become smaller games made by indies or smaller studios that will be released ever so few and far between (which already happens now). Sad. Very sad.
Hopefully word of mouth will help to make the game sell better on the long run, but it still is very disappointing.