Just throwing this thought out there. I happen to enjoy my Wii U. I think of it as a diamond in the rough.
I don't think they could lure back the third parties. It's too late for that. Also, the tablet controller isn't going to win the masses over with its innovation. It would have done that already.
They seem stagnant. Relying so heavily on the next Mariokart, the next Smash Bros, the next Zelda. There are few interesting things in the works, but it feels like they are just going through the motions for the most part.
I was thinking about this and it is a crazy thought I know, but what if Nintendo bought Sega/Sammy with all of Sega's franchise games? Reboot some of the classics. Dig into Nintendo vaults for games they have seemed to forget about. Do cross overs other than Sonic. Bring a stronger First party to the table to create some gems to draw more people in.
Buying Sega would be great publicity. Granted I don't know the state of Sega's design studios and what rights they have retained, if they would sell, or if Nintendo has that kind of capitol, but it's a interesting thought.
Maybe Nintendo could buy Hudson along with Sega. Get the machine going and really turn out some quality reboot/remake/new titles. I think that if the Wii U is to last anymore that another year or 2 they will really need to generate some helpful publicity and push out some consistent and more frequent quality first party titles.