I think Twilight Princess is using a heavily modified version of the original Wind Waker engine, at least, that's what I remember them saying at some point. But I assume you want them to reuse the graphical style, mainly.
What do I want to happen before next-gen? ... I want Twlight Princess to come out, with no big "problem." No unexpected gimmick present throughout the entire game (I'm not talking about the wolf transformations, I'm talking about something like playing through the entire game with the Tingle Tuner active without choice), no bait-and-switch design choice because they didn't like how serious it was turning out. I want a true sequel, a follow-up of the Zelda series and the gameplay involved (which Wind Waker did do), instead of losing the point of a sequel by trying to design a new gameplay setup with an existing franchise title.
Basically, I don't want a reason for people to complain, or push away the game. I want the biggest complaint to be that they didn't pick the "right" art for the box, no matter what they go with. We know there's going to be a Premium edition, so maybe people will say they're overcharging for the extras in that. But I don't want to be two months away from the game's release, and find out that they've kept a major, constantly-affecting gameplay aspect away from us, one that completely shakes the Zelda gameplay core. I don't want people to say, "This Zelda is broken because they're always making you [x]."