Even if it was just a movie, they'd to have blueprints on how they made it; why scrap that when you could put it to good use later? I'm sure Nintendo probably has a stash of unreleased stuff that could be used if the mood strikes them.
I wonder where people are getting the notion that Oot was all dark, moody, etc. Granted when you (spoilers for all 4 of you people who havent' played Oot, just playing it safe) Became an adult and saw Hyrule bazaar in shambles, the Kokori villiage overun by deku plants, saw no Gorons before the fire dungeon, and saw no Zoras doesn't mean Oot was all dreary etc. There was always that ray of hope.
All the chaos happened after the fact, we didn't see it in the proccess. Same thing with WW, we didn't see Hyrule get destroyed by Ganondorf or the Gods flooding the kingdom. So when people are quoting Oot as the base for a darker Zelda, I don't see where they're coming form.
NOW if you're talking about an adventure starring an Adult Link, similiar to Oot, but just higher polygon count, that's a whole different story. I just don't see Link slashing the innards of a Moblin or seeing a trail of impaled Hylians on the way to Ganon(dorf)'s tower. It'd be highly doubtful we'll see a complex relationship between Link and Zelda, most likely they'll just remain friends who are either too timid or too focused on saving the world as opposed to hooking up. Mario's been saving Princess Peach (or Toadstool) for how many years, and the two aren't officially an item? Bad example I'm sure, hopefully you know what I mean.
Obviously, Adult Link seems to be in high demand. The high sales figures of the 'Cube version of Soul Calibur 2 show this. So Nintendo should know that there is spot for him somewhere...