It would be my dream if Nobuo Uematsu did the Zelda soundtrack, but I think he's about as old as Koji Kondo, so it doesn't exactly answer the question. If I had to choose a younger composer, it would probably be Harry Gregson-Williams (MGS series) or Jeremy Soule (Elder Scrolls series, Guild Wars series)
When Koji Kondo dies...there will be no replacement. In fact, he should probably start experimenting with cloning techniques now, so that we will have another Koji Kondo by the time the first kicks the bucket. Surely I loophole will be created in the International Law preventing human cloning for such a important situation as this.
I agree with Aelic. Nobuo Uematsu did the music for many of the Final Fantasies, and they are some of the most beautiful soundtracks I have ever heard. And if they did the live orchestra thing for the next game and it was by Uematsu... I think I would die happy.
You guys.... I'm really disappointed that nobody suggested the lovely Eimear Noone. Shame on you all!
Eimear Noone is popularly known as the conductor for the Symphony of the Goddesses tours, but she's also a composer... a very, very talented one. I think that Eimear, who loves the Zelda series and can truly grasp and appreciate its music, would be a perfect fit. I love Koji Kondo's work and I never want him to go away, but he won't be around forever. Plus, he doesn't do all the music himself anymore anyway. Pay attention to the credits, and you'll find other skilled composers listed.
Anyway... EIMEAR NOONE! She's talented, she's familiar with the series, and she's also married to Craig Stuart Garfinkle who is a successful film and game composer as well. So, she'd be able to share her ideas at home- an opportunity few others that position have.
If anybody, I say Hans Zimmer. I know he is a movie composer, but I feel like some of his music could fit a Zelda game.
Plus, I'm a little biased towards PotC2... It is my favourite movie, and has my all time favourite movie soundtrack. Imagine Davy Jones' theme as some sort of epic final boss fight or something!
Kondo did one track on Skyward Sword, so really now is the time for someone new. I love Nobuo uematsu's compositions, he has worked for nintendo before composing the SSBB theme and I think he would be perfect for Zelda, if Kondo is not going to compose much for them anymore.