Right now Nintendo's 3rd parties need to be convinced. They think that the Wii U will flop and they aren't having much faith in the console. They feel that it is outdated(which to an extent it is) but I think gamers should be more concerned with gameplay and the fun of the gameplay rather than how many polygons a character can hold. The Wii U is a more than capable system. Nintendo just needs to do what they did to 3DS.
1.) At least a $50 price cut. The 3DS's success was hindered by a horrible price basically saying that this is just as good as the Wii when it came out, which can be debatable. However the thing didn't take off until the price cut.
2.) Great first party software leads to great third party software. Third parties such as Bungee know that the install base on PS4 and Nextbox will be huge so they are just going with it. With Nintendo you don't know what will be the trend. Motion controls, regular controls, a Gamepad? Who knows? So as always Nintendo needs to first flesh out the install base of Wii U before third parties feel safe on releasing a game on Wii U. Nintendo has again always been a family oriented gaming division, hence the Family Computer(Famicom/NES), so third parties are also keeping that in mind.
3.) Market the thing! If there was one thing the late 80's and early 90's video game market did it was market their product. With Sega's insulting commercials it made some people turn away from Nintendo and form the first company fanboys. That's a good thing. There's nothing like a little competition but the Wii U's marketing campaign is terrible. They need to make sure to specifically market Wii Street U, TV offscreen gameplay, and the unique ways of playing. Meaning that you don't have to play with the GamePad! there's a Pro controller which looks alot like Xbox's(which kinda ticks me off seeing that an updated Game Cube controller would work much better.).
So I'm not worried about Nintendo's third party support. They said they have all they need right now and I trust them on that. They've been handling with third parties since 1985. I don't think they'd just lose their savvy just like that.







