Alright, think about it, guys:
In the reveal, Link was chased by a giant robot that was practically vomiting lasers at him.
His bow also had some bad-ass technological arrow (I feel these will be the return of magic arrows, just not... magical).
Skyward Sword had ruins of an advanced civilization, complete with robots bearing advanced artificial intelligence.
When you explore the dungeon (the first one in the desert), and get in those little time bubbles (forget the real name), or get blanketed in the effect, time moves backwards, and you see all of these colorful neon lights, laser traps, high-tech versions of enemies, and so on.
That is Hyrule in the past, some time before Skyward Sword.
NOW, how am I certain Zelda U takes place THEN rather than in the actual future?
Simple...
Link's tunic.
There's a reason it is how it is, guys, and that's because the "hero's clothes" didn't even exist in that time period.
Skyward Sword showed the origin of both the Master Sword AND Link's famous tunic. The origin of the tunic was, quite simply, that it was a standard uniform for Skyloftian Knights.
That's all it was. Link wearing it for the first time in Skyward Sword pretty much made it this sacred thing passed down to his descendants.
This is why Link is wearing a different tunic, and not the famous green one.
It didn't exist as an article of clothing when Zelda U takes place.
So, now put it all together:
Technology seen in Skyward Sword ONLY when you go back in time, and the absence of the green tunic?
Yes, exactly. Feel free to let your mind implode now.
And as for the blue tunic resembling Wind Waker Link's starting outfit, well, I am going to assume it's a timeless outfit in the land of Hyrule worn by many people throughout time.
I agree that it had a futuristic feel. Either it's a prequel to Skyward Sword (before the islands were lifted up into the sky) or something farther in the future.
Both of those are a possibility, but I'm definitely leaning more towards it being a Skyward Sword prequel.
It all connects so perfectly, lol.
I agree, it's going to be about how Demise got imprisoned in the first place.