Ok, as I see it being mentioned again and again I'm gonna talk about it for a bit:
"Nintendo just going third party" is not nearly as simple as many of you seem to think, not to mention that it also likely wouldnt be good for them.
First, the obvious points: Nintendos Developers are used to work very close to the hardware, thats why their games are so performant and polished. Going Third-Party would cancel that advantage. Of course they would get used to other hardware, but it would never be on the same level AND it would take quite some time.
Some people here seem to honstly think all Nintendo needs to do is press a big red "Third Party" Button and *Boom* just like that we all got zelda and mario and smash on PS4 and XB1 and PC.
In reality a shift to third party would mean several YEARS of no or mediocre games until they get used to the new hardware and have shifted their development routines accordingly.
Secondly, and this ties in with the first point, they would likely loose many of their best people. Especially the veterans, people like Miyamoto, Aonuma and Sakurai are deeply rooted in the Nintendo of today. Hell Miyamoto could just go and say "I'm retiring" hes already at the age, he just goes on because he loves his job there. Being faced with changes on a level like this I think it is highly likely that they and quite a few other people as well would simply say:"Fuck this, I'm out!"
They would probably mimic Kojima, Inafune & Co and just open their own new studios, doing whatever they want.
Thirdly, and this is the part most people dont get:
They would loose tons of money.
Thats right, going third party would actually LOOSE them money!
Why? Its simple: Royalties!
Every Developer pays royalties to the platform holder so he can publish his game on the platform. Nintendo actually introduced this system back in the day, so they could stop the crappy shovelware that crashed the gaming industry from pulling them down.
Not only would they loose the royalties they get paid by other publishers, (remember there is still a bunch of third party on the 3DS!) they themselves would need to start paying royalties. I dont have the full numbers right here, but to put it bluntly their games would need to perform extremly well from the beginning and sell better on third party than they are selling now on their systems, which, at this point in time, is not likely.
I hope this helped some of you to realize that "just going third party" is not magically going to solve all of Nintendos problems.
tl,dr: Going third party would HURT Nintendo much more then it would benefit them.