So, Zelda U is supposed to release this year, but let's assume that NX doesn't release until holiday 2017 and Zelda U is one of the games release titles.

What do you do?

Buy it when it releases for Wii U (you can't wait another year).

Wait and buy it for NX.

Double dip and buy it for Wii U and NX.

Well if it was going to release for the NX, Nintendo most likely would not announce that until after Zelda U had a few months on the market to maximize sales.
But honestly it would depend on what the NX version would offer for me.

If there is an NX version, unless there are a bunch of exclusive features, including things like 60 FPS @ 1080p (assuming the Wii U version runs below this,) then I probably won't double dip.

Since the Wii U version would probably become rare like the GCN version of Twilight Princess, I'll probably end up double dipping. Especially if there are some big differences between the two versions.

I'd eventually get both but not at the same time. Wii U would come first unless there were other compelling reasons. Like if NX came out this year and had killer apps at launch. Then I'd get the NX version first.

If the NX version was substantially better and the NX was attractive enough for me to buy at launch, I would wait. Otherwise I would just get it for Wii U. No way in heck I've got the money to double dip.

Buy it on Wii U and more than likely won't look twice at the NX hypothetical NX version. Easy choice as I have never bought a system at launch or even close to it.

I still have my doubts on this game being released on the NX, but if that is the case, I would only get the Wii U version

I'm in the ''maybe'' category on getting it on both systems.

I don't think I will. I'll get the Wii U version and be happy with it. Its what I've been waiting forever for. Besides, what happens if NX uses that weird controller with no buttons like in the controller patents? I'd much rather play on the gamepad than that.