It was confirmed to be shown this E3, in fact they were going to show it last year E3, so it might be deep in development.
Confirmed from Nintendo doesn't really mean anything.
Pikmin 3 was confirmed to be coming to Wii.
It would be unheard of for a modern Nintendo console not to see a Zelda, but at some point they have to realize the investment isn't going to see great returns. So I see a few options. Nintendo takes the loss and releases it for WiiU, Nintendo shifts the title to their next handheld, while releasing a LBW like affair for WiiU. Something with the highest likelihood of seeing a good return on investment.
So I still say there's a chance large scale Zelda won't actually release on WiiU, and if it isn't actually shown this year I put the likelihood at one releasing at nil. I mean a large scale 3D Zelda is all but assured to be their highest dev cost ever. Just as Twilight Princess and Skyward Sword were before.
If it isn't shown this year for WiiU the best hope you can have is that it's a crossplatform title. Releasing for both WiiU and Nintendo's next handheld system.