So, basically you are saying that Nintendo staff is full of incompetent programmers. We've seen dozens of remasters lately so why would Zelda U be any harder to port to other console? Answer is that porting game is much easier than you think. We've seen a lot of PS2 remasters on PS3 lately and PS2 and PS3 are completely different. Probably even more different than Wii U and NX will be.
And you could make game for both consoles at the same time. Even Nintendo can easily develop game for several consoles at the same time and release it simultaneously. Heck, any big developer can do that so why not Nintendo. Nintendo might even make Zelda U and Zelda NX at the same time and that wouldn't even be a problem.
And how can know that they haven't started making Zelda for NX already (either a port or completely new game)? I'm sure they have started making games for NX already. Game development for next generation console has always started 1-2 years before console has launched. If they wouldn't start developing that early, then there would be no games for first year at all.
