Pikmin 3 released three days ago in Japan, and it's already proving extremely successful during the Wii U's time of struggle.
According to Japanese site ManTanWeb, Pikmin 3 is the hottest seller in Japan right now, or at least at major retailer Tsutaya. The retailer's Director of the Game Rental Planning Group made the following statement:
Pikmin 3, that came out nine years after Pikmin 2, is having a really good start. Sales at Tsutaya are comparable to the release of Super Mario Bros U and have driven greater sales of Wii U units.
Pikmin is just one of several major Nintendo IPs that are critical to the future success of the Wii U. Many argue that it's the console's $299/$349 SKUs that are giving it such a difficult time, but people are willing to pay that amount if the games are enticing enough. Even without a price drop the Wii U has a major price point advantage over the $399 PS4 and $499 Xbox One anyway.
From here on out the Wii U will continue to receive a consistent stream of exclusive titles. In September there's The Wonderful 101, in October there's The Wind Waker HD, and in December there's Super Mario 3D World . The questions that remain are if it's too late, and if the lack of third-party support will overcome Nintendo's expansive first-party library. If history is any indication, it's far from over.