I think NX will be 14nm and was originally going to launch in 2017. (The following is my view of events leading up to NX launch in 2016)
Thinking back to 2014, Nintendo was confident that they could turn around Wii U sales, they had just launched Mario 3D World and was looking at Mario Kart 7 and Smash 4 Wii U to "save" the Wii U. Their E3 was huge and they had momentum going into the holiday, during fall 2014 they started hardware development of the NX, at this point they figured they would keep Wii U for 3 more years and launch NX in 2017, so they picked technologies that would be ready in 2017, Nintendo uses withered technology anyways and this was a safe bet for them.
Holiday 2014 killed the Wii U. The big indicator is E3 2015, they clearly were moving away from Wii U, yes they launched Splatoon, but they didn't expect it to be a huge hit that it ended up being, Mario Maker a clear system seller was also not something Nintendo really believed in at first, they just couldn't bet on the Wii U anymore. Even Miyamoto was stunned by the low sales of the Wii U sighting that it has never been that bad.
A tough choice had to be made, the promise Nintendo made in Holiday 2014 about Zelda had to be broken, Starfox Zero is to save face with fans, but most content has already been moved over to NX.
Zelda was probably delayed for NX launch, though it might have been delayed out of 2015 anyways, considering that Zelda titles almost always are. They took their time to add voice acting and a female version of Link, not to mention that they probably spent the extra year polishing the hell out of the game. Anyways...
So holiday 2014 happens, Nintendo realizes that Wii U can't be saved, they change their gameplan, they can't support Wii U 5 years with 3DS's falling sales, they will have to push back Zelda and move up software development of NX titles for launch, they have to port Wii U games to NX and extent Wii U's software with DLC through it's biggest games. Splatoon, Smash, Mario Maker all get longer DLC support than originally planned (IMO)
Because of this change to NX's launch date (Yes I don't think mid 2014 Nintendo thought they would launch NX by the end of 2016) NX carries more modern technology than we are probably use to seeing from Nintendo, because it is a year earlier than originally planned. I think 14nm, Polaris, LPDDR4 256bit (136gb/s I think) are all very possible with NX and it actually makes more sense considering the context above.