Ok, crazy theory here...
What if this person...
Is also this person.
As mentioned before, the first scene appears to take place in the ToT and the scene with the old Sheikah lady also appears to take place in the ToT (but more like the one seen in
TP). At the start of the video when Sheikah girl walks through the golden light I think it takes her and Link to the
TP-like ToT where we see the old Sheikah lady (Sheikah Girl) waiting. Basically, the old Sheikah is Sheikah Girl's true form, she's just gone to the past from a request from the Goddesses, to save Zelda or whatever.
Old Sheikah and Sheikah Girl have quite a few similarities in appearance. Most noticeably, they both have a long pony tail. This may not seem like much, but they both have a red band tying up their pony tails. I can't really say much about Old Sheikah's pendulum pony tail apart from pendulums are to do with time and she may be able to travel through time.
And do the black and gold clothes that the old Sheikah is wearing look familiar to anyone else?
The dark blue and gold Old Sheikah is wearing over her black and gold also looks very similar to the top and trousers we see Sheikah Girl wearing. You can also see a cream coloured tear symbol below her eyes just like with Sheikah Girl.
As pointed out by Crazyfreak, the Old Sheikah is wearing the same bracelet that Zelda is wearing when she's in her white gown. Maybe Sheikah Girl gave it to her in the main timeline, but we see it with her in Old Sheikah's real timeline. If this whole time travelling Sheikah stuff is true, I can already see that this will be a ♥♥♥♥♥ for anything concerning the timeline...
We've seen time travel before in the ToT with
OoT and
TP. The
OoT ToT is kind of irrelevant here, but the
TP ToT brings up some interesting points. In
TP, Link walks through the door to the ToT and it takes us back to the ToT when it was in better condition (the one we see at the start of the trailer maybe?) and then in
SS we (kind of) see Link walk through the door/golden light which takes him to the ToT much like the one seen at the present day of
TP. Maybe the door can only travel Link from these two different points in time?
Sorry it's so long, but I really think I'm on to something. Has anybody noticed any other connections between Old Sheikah, Sheikah Girl, and both of the ToTs in
SS and
TP?
TL;DR - Sheikah Girl and the old lady in the trailer are the same freaking person, OMFG!!
Well maybe...
Wow, I didn't realise how fun speculating future plot details is
