KHIII immediately succeeds DDD so why should sora be any older?
new clothes? - probabaly (mr nomura even confirmed this)
aging? - nah
(sora does not sleep for another year - and the princesses didn't age since bbs either-
I suppose their aging will faint into some infinite timeloop like they did with the pokemon saga - ash is traveling for years and still 10
)
after all, if the characters change their physical apprarance too often they lose their value of recognition (if snow white gets a new sparkly dress that's good for selling merchandize - if she aged into an old lady (since 1928^^) new fans wouldn't even know who she's supposed to be. Disney's all about recognition and iconic heroes - they won't accept the idea of a grams-sora.
pixar worlds are pretty playful too. The only franchise that would fit into a grown-up keyblade weilder's world would be marvel but i pray they won't ever use them as they are so stilized and different in style.
They would rather inteoduce older co-characters (they sort of did with aqua and terra)
Disney has still so many workd to offer:
treasure palnet, pirates of the caribbean, princess-frog, tangled, american dragon, kim possible, phineas ferb, (the whole tv franchises), black caulfron, jungle book, 101 dalmatians (puppysora - wouldn't attract half the swooning fangirls as dogsora)
Emperor's new groove, hawaii-stitch, frozen (we need a snow-world)
oswald the rabbit!! Brave, monster's university.
combine both!
and aqua would be in her 30s by now - hence not good for appealing to the fans - world of darkness as loophole xP
so, heads down, no agong in KH except for sora's 2 forms he already has
imagine a grown up sora (woth japanese manga-style goatie xP ) hurling around with Pooh, goofying around eith Donald and Goofy, crying for his (wife?) Kairi...
nah, if that ever happens, I'll deny those titles and stick to the old saga.