Lets calculate the probability:
1. NX needs to be release in 2016. Nintendo never did this (annoucnement and release same year). Nothing hints a 2016 release. I give this a 50% chance to be true; 50% 2017 or later.
So you mean if NX is released in March 2017, Zelda WiiU can't be released for it? Or are you refering to holiday 2017 when you say "2017"?
And Sony never did an announcement and release in the same year either until 2013. I like that you're analyzing things like this. But some constructive criticism if I may. "They never did it before" is a shallow analysis of that situation. You need to look at why someone would do that, and how it can relate to Nintendo's situation. That's what determines what's more likely or not, because they're not just sticking to a pattern for no reason. There's a reason behind those decisions. For example, if things are going unexpectedly bad for the current console, and the company decide to move up the launch of their next console, an announcement closer to launch may be unavoidable, or impractical. If the decision to move up the release of the next console was recently made, chances are they don't have enough info about it to do a proper reveal the year before, as they just started speeding up the R&D for the next console. On top of that, announcing your next console has a negative impact on sales for your current console, so you don't want to do it as soon as possible without a proper reason. For example, if they feel they stand more to gain by making an early announcement. Square Enix announcing their interest to port Dragon Quest XI (a Q4 2016 release) to NX may be one example of such a benefit.
There are actually a ton of things pointing to a 2016 release. I would say practically everything does right now. But that's a different topic, and too much to list in a Zelda WiiU topic. But I'll shortly say that Nintendo's displayed support for the WiiU is something that heavily points to a release sooner rather than later. Nintendo actually haven't shown any indication of beginning any new meaningful support for the WiiU in terms of software since early 2014. The last time they announced any new quality projects for it was mid 2014 at E3, and development for those games started at least a few months before that.
Every single Nintendo title for WiiU in 2016 is a delayed game from 2015, except for Pokken, Which was an agreement signed in mid 2013, so that is by no means an indication of Nintendo's continued support for WiiU in terms of new software, but rather Namco honoring the contract they signed in 2013.
The only thing Nintendo seemingly began developing for WiiU since early 2014 is Amiibo Festival and Mario Tennis. Two rushed budget titles.
This is a very bad sign, as it's now 2016, making it around 2 years since the last non-budget title began development for WiiU that we know of.
This points to it being very unlikely that Nintendo will give it any more quality support in terms of new software. They're already treading the waters in 2015 thanks to delayed games from 2015. But there's nothing left to delay into 2017. And if no new quality announcements have been made since mid 2014, chances are they never will again. Pikmin 4 however was announced since then, but they oddly didn't mention what system it would be for. Also not a good sign for the WiiU having a 2017. I'm sure they'll make something for WiiU in 2017, but it will likely be something along the lines of Amiibo Festival and Mario Tennis. Not a quality title. Nintendo seemingly moved all their available teams to work on NX some time in 2014.
2. NX needs to be a home console or a combination of both. 3DS is older then wii u. It will get a successor first. So only chance is, NX will be the fusion concept. That could be right, also couldnt be right. We dont know. Nintendo said, NX wont replace Wii U and 3ds, but they also said the same about DS wont replace GBA. I think its a 50% chance that NX will be a replacement for wii u and 3ds (and will be powerfull enough to run zelda wii u).
Right after E3 2015, Reggie said that they've already publicly announced that they're hard at work on their next home console. When companies start talking about their next console, release tends to be not too far away. If it were to release in holiday 2017, that means he talked about it around 2,5 years before it released. In contrast, Sony denied the existence of PS4 until the very moment they stood on stage and unveiled it. Either way, Nintendo's next home console is on the way, and while I can't imagine why t wouldn't be part of the NX project, especially since I don't recall any other public announcement they've made that could fit the description Reggie gave, whether it is or not isn't relevant, the point is we know a console is on the way, and since they've already started talking about it, release should be sooner rather than later.
Regarding "3DS is older then wii u. It will get a successor first", that's also a shallow analysis. Again, you need to look at the reasons behind it, and compare to the situation. Systems don't get replaced based on their age alone, but based on how well sales and software are performing as well. If it was as simple as your reasoning, then PS2 would have been replaced before the PSP. After all, "PS2 is older than the PSP, so it will get a successor first". But that didn't happen, did it? No, because PS2 was a huge success. The biggest ever in terms of a console. Now what parallels can we draw from that to the WiiU's situation? Well, the WiiU is actually the worst selling console of all time (between Nintendo, Sony and Microsoft). So base your analysis on that instead. Age is one factor, but it's not the only one.
I do like how you didn't take their "NX won't replace WiiU and 3DS" comment for face value by comparing to their statement about how DS won't replace the GBA. Just like any other company, they will tell us things in ways that are most beneficial to them. Announcing new consoles has a negative impact on current console sales, so saying things with a twist like this can dampen that effect, while also sparking more interest for what the new console may be.
3. Nintendo needs to want to release Zelda Wii U on NX. Even if both points above turn out to be true, Nintendo also needs to want a cross release. It was always a unwritten rule, that every home console system from Nintendo will get its own Mario, Zelda, Mario Kart and Smash game, The 4 big home console franchises from Nintendo. This wont be the case for wii u. Considering Wii U´s low sales and all the Zelda remastered and spin offs it got (Windwaker, Hyrule Warriors, Twilight princess) it may be likely they want to compensate this.
There is one point however which stand against this. All 3 mentioned zelda games (HW, WW, TP) were released, or at least in development before Zelda Wii U got delayed. So assuming Nintendo brought this 3 games to compensate the lack of an exclusive wii u title doesnt make sense. Windwaker was released 2013, HW 2014 and Tantalus already spoke about their Wii U Remaster in Dec. 2014. In Dec. 2014 Nintendo told us Zelda will arrive 2015. So all 3 games arnt made to compensate Zelda Wii U´s cross release.
First off, Tantalus actually spoke about their Wii U port in January 2014: http://nintendoeverything.com/tantalus-media-starting-work-on-aaa-next-gen-title-this-month-wii-u-mentioned/
But that stands to your point, which I agree on. I don't think the Zelda titles for WiiU were made to compensate the lack of an exclusive Zelda game. I think Nintendo simply had a lot higher hopes for the WiiU. I think the question is, would Nintendo want to release Zelda WiiU only on WiiU to compensate for there being a lack of an exclusive Zelda title on the console? You have to wonder why they decided not to show us more from the game, when they said they had plenty of content they could show in 2015, but decided not to. A question I still don't know the answer to, because they wouldn't have to reveal any unique features that the NX may be capable of. They coud simply show the WiiU version. (Just like if Nintendo showed the GC version of Twilight Princess, we wouldn't have any clue of there being motion controlls in it for another version.) So I don't know why they're not showing it, but it is a curious decision none the less.
Anyway, when the NX launches, having a Zelda title at launch would be a big selling point. They are probably trying to avoid a repeat of the WiiU's launch where they didn't have a Mario, Zelda, Mario Kart or Smash available for over a year.
Ideally, Nintendo probably wants each of their consoles to have a unique Zelda game. But the situation for WiiU is less than ideal, so some times things just don't go as planned, and they have to make some moral sacrifices in order to make sense from a business perspective.
I don't know what percentage I would put on an NX version of Zelda WiiU. At least not from analyzing facts. Because Nintendo don't usually do what makes most sense anyway. But I do feel there's a good chance of that happening. And there's also recent discussion about Smash ported over to NX including all the DLC, due to all the content they've invested in the game, such as the third party deals with for Cloud, Ryu, Megaman, Bayonetta, etc.