I think there's a lot left to do new with the vague concept of "open world" tbh. That is where Zelda U still has the chance to impress people, even in a post-Witcher 3 world. When people complain about open world games, it's often the lack of meaningful quests and the padding in form of empty space you have to run/ride through to get from A to B. Even in a highly regarded game like Witcher 3, the world itself was pretty much non-interactive. You have your map and see some symbols on it, you go there, and it is always a bunch of red dots popping up, marking enemies that you have to defeat. Despite the vastness of the world, there's almost no sense of awe and wonder (maybe the one big exception: the swamp village, the witches and "that tree"; loved everything that happened there).
This is where Zelda U could re-define the concept of "open world". Now, this is not to be mixed up with what Skyward Sword did, because Skyward Sword is the worst 3D-Zelda-game, completely forsaking its overworld in favor of turning it into an artificial puzzle environment (and it is the Zelda that broke the "Zelda cycle", because I know many people, myself included, that ever since the initial playthrough have never touched it again). What I mean is a world that is filled with mysteries, not traditional puzzles.
For example, I loved how in Ocarina of Time there was a hint on some stone at Lake Hylia that would lead you to shooting an arrow into the morning sun, giving you access to fire arrows. That was a magical, whimsy moment. Same for when you were exploring the Lost Woods and, without being told to, find some skull kids that lead you to a sidequest with a heart piece for a reward. Another favorite moment of mine is when you, in TWW, reach Ichtusk island and you find out that it has been attack, you're too late, everything is destroyed. Despite nothing "happening", it gave me the shivers, imagining what gruesome stuff Ganondorf did here without anybody intervening.
All of those examples could me multiplied by the factor of 10 or more, to fill a vast world with meaningful secrets. And a new kind of puzzles, while we're at that. I have no interest anymore in the sort of puzzles that SS threw at you. Collecting five golden key pieces, collecting tad notes, etc. - I'm tired of those abstract, (again) artificial, "gamey" elements that take you out of the experience and remind you in such stark contrast with the beautiful environments, that you're playing but a video game. In a post-Portal era, I'd like to see the Zelda-series adopt more believable, natural puzzles (i.e. instead of pushing boulders or collecting "stuff", maybe there's a lava river and you can use ice arrows to freeze it. But you can also use your power gloves to push a giant rock into the river to stop its flow. Or you can use that gliding cloth from what we already saw to fly above the stream of lava. The point is: Have the player experiment. Not force "that one, and only ONE!" solution on us. Having only one way to solve a puzzle often leads to frustration and dead ends, punishing the player for exploring the world), as well as incorporating ingame-lore and hearsay to take as hints for more mystical puzzles (think of the fire arrows puzzle, except more elaborate, lengthier).
When I think of what kinda atmosphere I'd like to have in Zelda-games, I always think of the animated movie "The Last Unicorn". That's the kind of mix of whimsy, magical, but also dark and dangerous, brooding. So, I think there's still a lot to do with "open worlds" that has not been done, yet.
(Hi, btw., my first posting on GAF after waiting many months for activation. Kinda nervous, hope my first post didn't offend anybody :>)
