wii u had a good bundle this year that was discounted to the same price bundles were discounted to last year (although during december and not black friday). the platform hasn't had an actual price drop since before the other two 8th gen consoles launched. to top it off, the wii u didn't have any sort of high profile game for november, just multiplayer family stuff that traditionally sells best in the holiday, but isn't the sort of thing that garners interest in your console. zelda, and then star fox, were supposed to fill that role, and both were delayed.
the wii u should be doing worse at this point, with all that considered. and it can be doing a lot worse - i think the vita shows there's room to slide. 2015 is probably going to end up with a small dip in sales after 2014, but i think 2016 is where we'll see real decline. it'll be back to 2013 levels or worse, at least until/unless nintendo decides to fire sale remaining stock at $199.99 or something. i can't see this thing on the shelves in a major way in 2017 at all. 2016 will be its final holiday season.