Rumors have been floating around that NX would be out in 2016 and Wii U production would cease when that happens but Nintendo finally announced some clear details. NX is scheduled for March 2017 and isn't meant to replace the Wii U or 3DS and the new Zelda game will be released at the same time for both Wii U and NX. Also, they stated the only thing they would be showing at E3 this year will be Zelda (so another fairly weak year for Nintendo at E3 I guess).
Take that for what its worth but I feel better about moving forward with my game meant to include gamepad play and not get surprised by a replacement system in 2016.