I don't see the problem with it. I'd even be perfectly fine if they made Link a woman, or gave him a new black haircut (not like
game companies have ever done that, of course). I don't particularly see what's wrong with change in a video game series so long as it adheres to its core roots, and believe it or not, Zelda being medieval is not one of them. The point was to get lost in an epic fantasy adventure, not just to put a sword in a guy's hands and tell him to do crap for no adequately-explored reason. To that end, Zelda could be medieval, futuristic, or prehistoric - it really wouldn't matter so long as it kept the other core concepts intact.
I also don't think a futuristic Zelda is "unnecessary" or "just a rehash." I and probably many others are legitimately curious to know what Hyrule would be like in modern times. How would the Gorons mine for rocks? What would happen to the Gerudo? What kinds of items and puzzles would Link discover? How would Ganondorf/generic threatening villain take over the kingdom? How do people still view the Triforce? If a modern-day Zelda is unnecessary, then so were 3D, cel-shaded graphics, or portable Zelda titles. None of them needed to be done, but were arguably of great benefit to the series.
So yes, I support a modern-day Zelda wholeheartedly and would love to see Nintendo take a stab at it. No, I don't want Zelda to change its core values or remain modern-day forever, but a game or two in that light would be a nice change of pace. The real obstacle is getting it past the rest of the Zelda fanbase. DmC: Devil May Cry received very good reviews, but was deemed a commercial failure, probably because a lot of fans didn't get on board with the whole reboot concept. Zelda could just die if it did the same thing.