I certainly hope they will be a large part of the plot. If not, I hope that a little more light is shed on them.
I think it's safe to assume that Skyward Sword predates Ocarina of Time. After all, the Skyward Sword becomes the Master Sword as stated by Miyamoto, so that's more than enough to speculate the possibility of it being before the Hero of Time's quest.
I've been pondering.... Remember, Shad said that the Oocca created the Hylians... of course, this goes against the Zelda creation story, but it was never really that developed to begin with.
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"Yes, according to legend, Hyrule was made by the Hylians, who, as we all know, are the closest race to the gods. But also according to legend, long ago there was a race even closer to the gods, and some say THESE creatures made the Hylians." —Shad
"The common opinion is that Hyrule was created by the Hylia people, the race closest to the gods, but...truth be told, there's also a theory saying that in ancient times, there was a race even closer to the gods than the Hylia people, and THEY created it." — Shad
"When they created the people of Hylia, they simultaneously created a new capital, a city that floated in the heavens." —Shad
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What if Sky Loft is actually that new capital? What if it's the previous capital? What if it's the dwelling place of the Oocca, period? Link is supposed to be born and raised there, so... maybe this Link is once of the ancient Hylia? If it were so, then that could be a very interesting way to include the Oocca in the game and further expand upon their history. In Twilight Princess, Shad stated his knowledge was a
theory, so it's possible that he might not be right at all, and we were just seeing a glimpse into how legends become twisted and lost over centuries...
In any case, I think this would be a great opportunity to go into detail about the Oocca. They used to keep in contact with the Royal Family of Hyrule, and the Dominion Rod was used whenever they needed to speak to one another. However, they ceased communications, and I'd like to know why. This would be another great opportunity to get into detail about the sky being's relationship with the Hylians and the goddesses themselves.