Aye. Nintendo not only lost a ton of the "casual" market with the confusing name and GamePad (everyone had tablets, it wasn't novel nor interactive; IMHO they should have doubled-down on the Wiimote and made it even more accurate with some sort of haptic feedback), but they couldn't make up sales with their core market because they had nothing in their core franchises. Pikmin 3 and Wind Waker HD can only do so much, and NSMBU was just more of the same.
However, that's starting to turn around with a lot of their core (and some not) franchises on the horizon. The biggest is Super Smash Brothers (with the boring titles of "SSB for Wii U" and "SSB for 3DS".) The 3DS version comes out first, but WiiU looks to be early 2015 ("Q4 2014", currently). Super Mario 3D World and Mario Kart 8 both saw a surge in numbers, especially with the MK8 numbers posted for the past month. They've shown a new Zelda and have Hyrule Warriors coming out to tie over fans in the meantime. No Metroid or Star Fox, sadly, but those aren't nearly as big as Mario or Zelda. (And I'll take "no Metroid" over "Team Ninja Metroid" any day.) There are also some cult-classic sequels, Bayonetta 2 and Xenoblade Chronicles X, that will move less units but still create some fervor. (I'm holding off on buying a Wii U until Xenoblade Chronicles X, personally.)
Once the core franchises get core hits, sales will jump, and with those expanded sales might come more (competent) third party games, creating a positive feedback cycle. It won't be as big as when developers went "Oh shit!" when the Wii unexpectedly sold like hotcakes and started trying to pump out titles (leading to a glut of shovelware), but there is potential life in the Wii U yet.
I just hope Nintendo learns from their mistakes this gen (poor name, poor control setup, poor hardware) when the next rolls around.