There doesn't seem to be much that Nintendo can do at this point. I think they relied too heavily on the Wii U's unique gamepad selling the device.
Unfortunately unlike the Wii which offered a unique and revolutionary new way to game which was also accessible to casuals I think they went backwards with the Wii U. Basically if you are a core gamer who wants access to the majority of multiplatform games your best choice is either Microsoft or Sony or if you are casual then tablets and smartphones are an easy way to game.
The Wii U on the other hand is a bit intimidating for casuals IMHO. They should have either stuck with the Wii strategy or made the device more 3rd party friendly.
It is really unfortunate but at this stage Nintendo may as well ride out this generation while providing their usual 1st party support and then hopefully learn from their mistakes or possibly come up with a new effective way to disrupt the market and make a killing like they did with the Wii initially.
Ofcourse it also doesn't help that they named it the Wii U. If anything they should rebrand it and do a relaunch if possible with a huge marketing campaign.
