If it was for the end of 2017, Nintendo would not keep releasing videos.
Like this one last month http://www.gamespot.com/articles/link-rains-death-from-above-in-new-zelda-breath-of/1100-6443195/
It's coming first half of 2017, it's just that Nintendo doesn't want to talk about NX at all right now, and maybe they think Zelda is not a good game to have on launch. Nintendo plans to have a continuous stream of game releases in the months following the launch, so maybe Zelda will come after, in may. They're not going to release everything on day one.
The launch of the NX is not just one day, it's going to be from march to the end of the year.







