Nah. I think Nintendo's best bet would be to unify their library and come up with a console/handheld equivalent for their NX platform. People who want to round out their gaming library will just buy the cheaper handheld device and use it as a companion console the same way many PS3/360/PC owners used the Wii/DS last generation. Those Nintendo fans that want the full Nintendo experience would just opt to buy the console version.
I believe that if Nintendo went 3rd party, they'd lower output and focus their attention on their biggest money makers like Animal Crossing, Mario, Zelda and Pokemon because they'd no longer have a need to diversify their library and could focus entirely on what sells. Also, I could see Nintendo focusing a hell of a lot more on mobile than they would on consoles because of three reasons -- they pay way more attention to the Japanese market than the western market and mobile is huge there while the console market is dying. Console development would be significantly more expensive than just churning out mobile games and the demand for Nintendo games would be significantly better on mobile than it would be on consoles.
It's actually funny to me that a lot of the people who want Nintendo to go 3rd party are also the same console fanboys that constantly rag that all Nintendo makes are baby casual games that they wouldn't be caught dead playing. If that's the case, why would Nintendo spend the funds to push their games on platforms full of ultra serious hardkore gamers like them when there's another market that better fits their style on mobile?