Lets just put it this way. When the sublime Mario 3D World on an 'existing console with an admittedly small user base' sells far less copies than the 'its OK but nothing special at all' KNACK on PS4 - then you know the Wii U is in trouble.
I like my Wii U. But it's clear Nintendo over estimated it's ability to sell 'older/slower hardware on new consumers under the ever present threat of the PS4 / Xbox One launches' and now the new hardware is here - even killer AAA Mario game is providing enough of temptation to sell the hardware to new users or even to sell the game to existing users.
It's not good for Wii U.
Nintendo can ride it out as the 3DS is a cash cow, so they aren't going to die like Sega after the dreamcast.
*i think the Wii U has quite a few problems... the biggest IMHO was the launch price for the premium bundle ... it's more expensive than any other nintendo console at launch with a price over 300 price point (Wii: 249, including wii sports, Gamecube: 199 bucks)
*also as a Wii owner some decisions simply were confusing: Wii U supports the Wiimote with Wii Motion plus but not the 'normal' one, for those were friends have mostly classic wiimotes it meant rebuying plenty of controllers for party games
also with the step from Wii -> Wii U one could really amas all thsoe extra controller add on parts:
Wiimote, nunchucks, Wiimote Motion Plus, Wii U Tablet controller, WiiU Pro controller
it really fragments the install basis right from the start. They should have simply said: 1 controller = tablet controller + wiimotes&nunchuck for party games
*no built in harddrive & different SKUs: mcirosoft and sony both had multiple SKUs at _launch_ last generation and it was a stupid idea ... Nintendo went on to repeat that mistake.... also going with 8GB and 32 GB memory instead of a harddrive ? a msitake IMHO ... had they simply made 1 SKU with a 160 GB drive for 299 and they had have been in a better position
*also i don't get why they have never made a pokemon game(their biggest money press) for the home consoles ... completly baffeling
*why do we have 3-4 Mario jump and run games for the Wii U by now and no Mario Kart ? on DS,3DS, and Wii that franchise were combined with a bundle an ultimate system seller
* also: why make a windwaker HD remake isntead of simply making a brand new cell shaded Zelda ? ... it's hardly because they lack money in their pocket
* no new franchises/ big game ideas so far
* still no classic follow up for the board game Mario party games with great online support
i love my Nintendo stuff but since i'm mostly interested in their own games i currently _have_ to wait for a 199,- Mario Kart Bundle and some new stuff
edit: also something still sorely missing: AFAIK they still don't have that central account based online system is that correct ?