But will not reach PS4 level sales. Overall I think that with Zelda as a launch title, proper releases of classic games like a new 3D Mario, Metroid, NEW Star Fox (not a cheap N64 remake), 3D Donkey Kong, Pokemon, Fire Emblem etc we could see a very STRONG start.
Follow that up with newer franchises like Xenoblade and Splatoon with a few third party contracts for other exclusice titles, and the NX will be a success for Nintendo and in the end profitable. The reason it will not reach PS4 sales is because the PS4 has become the home for 3rd party multiplats. Just having those games on NX will not be enough to beat Playstation at this time, but Nintendo has more than enough IP (more than any other console maker) that with proper 3rd party support (NX exclusive titles) it will have a powerful identity as the console everyone will want ALONGSIDE their PS4 or X1.
I also feel that while the NX will not reach PS4 level sales, it could still outsell the NEO version as NEO will offer nothing new to the table, while the NX will be a whole new experience.
EDIT: To put a number on it, 60 mil. It will not sell as much as PS360, but will outsell the X1 and N64. It will also be profitable for Nintendo.