I'm sure the PS3's architecture was more different from the PS4 than the NX' architecture is from the Wii U. And yet, TLOUR was finished in "just" 1 year. It's not like all ports take as long as Tantalus's port will. It depends on team size, and I'm pretty sure if Nintendo releases NX in holiday 2016, the Zelda team will have managed to port Zelda U to the NX. For all we know, Zelda was ready for release this holiday, but was delayed to launch with the NX, just like TP.
Not saying it will happen, but it's not like it's really unlikely, or not doable...








