Seriously Zelda will not be ruined if it doesn't have voice acting, nor will it be ruined if it does. I don't see why this has to be such a heated issue for people.
The presence of voice acting requires a change to the writing approach in a video game. The sort of dialogue typically found in the Zelda series works very well for the text-only approach, but it would sound awkward and forced if voice-acted. If they want to maintain the same writing style, I've no problem with them eschewing voice acting. If they want to use voice acting, which I'm fine with, they'll have to take that into consideration while writing the dialogue. I think this is one of the reasons the gibberish approach interests Aonuma, because they could technically have everyone "speaking" without having to factor it into the writing.
Honestly, if ever there was a time for them to consider voice acting, this is it. The game is already huge, might as well go big or go home. And I do want to have voice acting in a modern Zelda game, just to see how it feels. I might like it, I might not.
Wait, I'm not saying that it will be ruined without VA. By favorite game of all time is a Zelda game without VA. My issue is that the lack of VA is an unnessecary lessening of it's quality for no trade off benefit. It might have been argued that, because VA takes up so much disk space, the devs chose a bigger and more explorable world in OoT, MM, and WW instead. I can get behind that. It becomes an issue for me in games like SS, TP, and especially, where disk space is no longer a limiting factor. There's nothing to trade off. Zelda can have it's cake and eat it too, but it doesn't for no good reason.
Dialog would need to be changed, but only slightly. There are plenty of cases where dialogue with Zelda's quirk and charm work. Studio Ghibli movies are a perfect example of this. Some weird ass characters say some weird ass things in those movies, but it works. Everyone knows that it's weird, but it's part of their charm. I don't think that Zelda's writing style would have to change much at all, and most dramatic and memorable scenes in Zelda games could have been untouched completely and have worked exceptionally as a script for voice actors.