I wrote up a post and then realized this was similar. I am going to post my speculation here, which will overlap some with what has already been said. So if you think, "I already said that" - yes, you did. Think of mine as an essay where I had to list my sources.
*spoilers for Sage/Master Sword related points in SS interviews and the TP, OoT, AlttP and WW games*
I was reading up on sages last night when I ran across this quote. Zelda tells it to you in Twilight Princess.
"There you will find the blade of evil's bane that was crafted by the wisdom of the ancient sages...the Master Sword."
We know from an interview that "The Skyward Sword will become the Master Sword." Barring a little misdirect (perhaps it's an obvious predecessor but the transformation doesn't happen in-game), if the series stays true to its own lore then it's a fair guess that sages will be part of the story somehow. Which brings to mind several questions.
How likely is it that they will appear? The TP quote says "crafted by the wisdom", which seems fairly explicit about their being the creators, but that could still mean that the spirit of the sword is blessed by the sages but they're in the background.
If they are in it, how big a role will they play? Will they have to be reawoken like in Ocarina of Time or become allies like in Wind Waker? And will we see any familiar names? Kaepora Gaebora is said to be the reincarnation of an ancient sage - perhaps we'll see his origin. Depending on how much time passes between games, though, there could be several generations of "ancient" sages, from different eras, and KG may not be from SS's time. Rauru also calls himself an "ancient sage", which could mean he is a survivor from a previous generation, or it could just be ambiguous wording.
My thoughts: I can easily see sages fitting into the setting. The farther in time you move from the origin of a legend, there will be more distortion from the actual story and less believers in it. But SS takes place early in Zelda lore, so not only would they be a natural part of it - they might not even be a legend in SS's era. They may simply be a reality to people of that time.
If they are a part of the story, I think part of Link's journey will be to find them, though not necessarily reawaken them. They'd probably live in the far ends of Skyloft, with Link having to travel to Hyrule and use certain 'warp points' (for lack of a better word - I know the SS will be his travel mechanism) to gain access to those sections of Skyloft. Perhaps they are trapped in those sections, or perhaps they are so far removed from others that they don't realize what's going on in other parts of the world and Link is the messenger.
The reason I see Link finding them is because I see two ways for the Master's Sword to become "the blade of Evil's bane." One is for it to be given as a gift from a deity, which means that it was sacred to begin with. Though the AlttP manual clearly says that
humans made the sword. So the other option is for it to be an earthly relic that was purified. If it's the latter, which it seems to be, the ancient sages would fit perfectly for that role, similar to how the sword was powered up in Wind Waker.
Their fitting into the story doesn't mean they will be in the story, of course - these are just my thoughts on how they could. Resurrecting this topic in hopes that other people have more thoughts.
