To be honest I think Nintendo is kinda content on the Wii U being what it is. It's not going to have some huge surge in sales, it will have some bumps now and again, but it's headed to about a 18 million LTD finish barring a miracle.
Zelda in November 15 versus Zelda in May 16 isn't going to change that.
What Zelda in May 16 does though ... it could allow it to also act as a launch title for the next Nintendo handheld. Which could be a really big thing for them, it gives them a big title to launch with and probably channels an extra couple of million in sales into the game. Something I don't think Nintendo takes lightly as it will likely be the most expensive Nintendo game ever made (gotta maximize its sales potential).
I think it will release in spring 2016 for Wii U + a launch title for the next Nintendo handheld.
