Zelda won't do nothing. For a console to succeed they need multiple games like Zelda and third party games. As for my estimation it will do Wii U numbers if PS4 Neo takes off smoothly.
Zelda alone will ensure a smooth launch. E3 will shed a bit more light on this, but I have a feeling it will be comparable to Witcher 3 in scope. Some people, like myself, will upgrade from WiiU to NX for this game. Most people who do not have a WiiU yet but want this game will go for NX just for the superior version (if my prediction on power holds up). See Twilight Princess sales for reference to this fact.
And of course there will be other games. Part of their strategy is to have a steady stream of games exclusive to the NX right out of the gate (why the WiiU is dead this year). It does not take a rocket scientist to see that.