It pretty much will be anyways. I mean who is going to buy a Wii U in 2017? 

It should have enough software that having a cross gen Mario game shouldn't make much of a difference. If having a few cross gen titles are going to sink the ship (and honestly, you aren't going to get many people to buy a Wii U in 2017) then they don't have a solid strategy anyways.

Any benefit they gain from pushing a few more software copies will be outweighed by the reduced incentive to buy the new system their future depends on, and the additional development costs of cross-gen production. Releasing only on NX is better for Nintendo; they sell more hardware, and they don't have to burden their already stretched workforce by working on two versions of their major games. Wii U isn't worth the investment at this point.

Not a chance.

I highly doubt the next 3D Mario will be a launch title, having Zelda+3D Mario at once isnt really necessary and they would be better off spreading major releases out. If I had to guess, I would say 3D Mario will be the big holiday 2017 title.

If one game can turn a profit, it's Mario. It's pretty much a 0% risk endeavor to make this a cross gen. As for reduced incentive to buy, who do you know is going to opt out of buying an NX for a Wii U in 2017? It's a non issue.

Disagree tbh they may as well just dedicate it to NX and NX alone because the will still be around 15-16m Wii Us out there compared to a newly released platform and Nintendo would want them to go out and get a NX. The's much more than 0% risk as they're leaving the Wii Brand behind to start fresh much like they started fresh with the blue ocean strategy when DS launched, making it cross gen is just further prolonging a brand they're leaving behind, Zelda should be the Wii brand's swan song and that's it.

Couldn't be all that different if Breath Of The Wild is releasing for both. As well as a new Mario game still being incentive to get an NX, it is, as the Wii U won't have much of a life left. 

It makes no sense to rob your new console (that you desperately need to sell) of exclusives. NX needs system sellers. That is vastly more important than squeezing a couple more software sales from a dead console.

BOTW was always commited as a Wii U game, they're just salvaging its potential by giving it a multiplatform release much like they did with TP, the new Mario game on the other hand was never commited to being a Wii U game at any point so it's not even close to being the same situation, the new Mario would have to be scaled down to work with the Wii U which takes more work than scaling Zelda up for NX. BOTW sees off a gen and starts a new one, after BOTW it's all going to be about the new gen platform and a 3D Mario is a suitable title to really kick off the new gen.

Wii U not having any life still doesn't mean it won't impact incentives for the NX, TP still sold 1.6m on GC after all and it release after the Wii version.