The Wii U has been out for seven months.
The WiiU has
consistently missed Nintendo's sales forecast (even after revision) and, after a very front-loaded launch, is
currently below the PS3's - a console launched at 599$ for the most common SKU and which, unlike the Wii U, had no risk of its 3rd-party support being jeopardized by upcoming, disproportionately more powerful systems. I've also read that the Wii U's been doing below both the 360 and PS3 worst ever weeks, but I'm having trouble finding an up-to-date archive of monthly NPD numbers.
Of course, it's possible Nintendo turns things around (and not in a "DROP GAMEPAD CUT PRICE TO 150 BUNDLE SMASH BROS THERE I SAVED YOU NINTENDO"-kind of way), when first-party games finally hit but it's pretty safe to say that the Wii U is plainly not doing satisfactorily at this point of time.
Third-party publishers who either had Wii U games come out recently or who have upcoming games:
There's support and then there's support, though. Sqeenix, for example, may have released a quick and dirty up-rezed port of a Wii game in one region, but is it really substantial support when they've announced two blockbuster releases for competing systems and basically nothing else for the Wii U?
I attribute it to this: Nintendo makes so innovative consoles that no other company besides themselves can figure out what to do with them.
As opposed to a combination of poor branding, featuring a quirky proprietary architecture while competitors are moving to more standard x86-based systems, extended first-party software drought caused by the chronic delay of "launch window" games (and that despite Nintendo basically abandoning its predecessor for the two preceding years, which should've guarranteed some time to get accustomed to HD development), mediocre launch lineup.. etc?
If the WiiU did well, the third-parties would make games for it, quirky control method be [darn]ed. Look at the DS.