It's been rumored to have been in development since 2011. Assuming that could be true, A 2014 ship date makes logistical sense given that both ALBW and Wind Waker HD are now in the wild. They've probably doing some work on it since they finalized the WiiU hardware.
Generally, Nintendo puts a new Zelda game on a platform roughly two years after that platform has been introduced.
I predict NX launches in 2017 - not 2016







