Just a quick couple of thoughts. I was going to post this in the other thread but they seem a little touchy on spoilers and I don't want to add something into that thread based on the Art book leaks.
I am almost certain now that Zelda is in the past on the Sky Islands. It makes the most sense to me story wise from what we know, or think we know. And it mostly revolves around the calendar/time machine we see her standing in front of in the trailer. We see the Sun dial and moon dials moving with a door opening in the center.
I am thinking we will have to repair or rebuild the one in the present eventually, but just the fact that we see it working and in operation vs what it looks like in its current condition is a pretty clear indication she is in the past.
I am guessing that the original Basket was done in by Gannondorf in the past as seen from the mural, which coincidently is the only portion of the mural that we know the least about.
We see Zelda holding Basket's Tear and saying "I know why I am here and it's something only I can do." So it makes sense to me that, for what ever reason on the how Zelda was able to go to the past with Rauru, that she needs to fill the role of Baskets' job before Gannondorf killed her. I don't think Zelda has any direct relationship to Basket but my guess is that it has to do with the Triforce of Wisdom that Zelda probably still possess.
Just speculating but the Calendar/time machine might also be a way to transfer objects back and forth through time between Zelda and Link.