I think it would be very cool to see the graphics from the Tech Demo in a future Zelda game. I myself do not consider graphics terribly important, but I would like to see a Zelda game with that style. Usually when I criticize games that are realistic, it is because that is all the game is focusing on. Take the Call of Duty franchise... they don't change the gameplay (which is fine, the games are fun to play every now and then) and they only way they can implement new ideas is by updating the graphics. It makes me feel as if I'm just playing the same game and all the ones before it were just betas to the latest one.
With all that being said. If Zelda was realistic that wouldn't destroy the series. It can still have a unique style while looking bad ***. What I love about Zelda is that there isn't just one single art style that it uses. It's capable of doing pretty much any style it wants to and yet it still feels like a Zelda game and they style fits said game perfectly.
As for the what I want in the Wii U Zelda...I wouldn't mind seeing how the tablet could be implemented. I mean I would love to have Skyward Sword's controls again, but I would also love if it went to button mashing again.The tablet could serve very easily as the inventory screen and map allowing the player to keep moving with out having to pause so often like in the remake of Ocarina of Time.
To linearity...I want Zelda games to have an epic storyline, which they do, but I mean epic epic. I want the story line to be complex and intricate. I don't want to be able to say oh there's Zelda (I'm talking to you Tetra). I want the story to surprise me and so to do that I want a new Villain. Ganon is great, but he needs to let more guys have their shot at Hyrule.
I also think that its time for Zelda to incorporate Voice Acting. Now I personally always name Link Link so I wouldn't care if they took away the ability to name him. I don't think he should talk, but even if he does I honestly don't think it'll be bad. Look at Metroid Other M. Samus had never talked till then and by giving her a voice, they gave her emotion and feeling, something that had been lacking from her character in the games. Now Link doesn't necessarily need to talk, because you can see his face due to it not being covered by a suit the entire time. His emotions can still be easily read. I don't want to have to see the characters move there lips but no words come out.
Lastly, and this is just a maybe, I wouldn't mind having a Zelda game starring Zelda. Now no one mention the CDi games, because I don't think a single one of actually consider them as real Zelda games. Having a game starring Zelda would open up completely new gameplay mechanics that could be more focused on magic. Maybe the magic bar could be useful again. I personally think it would interesting, at least as a side game and possibly a main game. But I don't want the story to be Zelda is saving Link...that would just be dumb.