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.
I am not so sure, Zelda Twilight Princes done great things for Wii reagardles Wii Sport, actually Zelda Wii version was sold out everywhere at launch. Definitely moved lotsa a consoles.
No one said Zelda will only big launch titles, new 3D Mario is also very possibly, and definitely there will be some other strong 1st party and 3rd party exclusives for NX launch or launch window.
Wii U didnt had nothing similar at launch, actually had weak launch and 1st year games.