Yeah, I got this info from both Palette and from Dogasu of Serebii forums. I'll put what I remember in my own words:

Ash's friends are barely in this episode. most of it is JUST Ash. This is another split-up episode. Anyway, contrary to the old rumors, Regirock was not in this episode. But I'm actualy happy about the plot. Basically, they travel in the misty mountains and come across ruins, and a young girl with a Baltoy. Her name is Kuruyo, and she has a lifelong dream of being an archaeologist. They also come across a mysterious woman in a red cloak who is an archaeologist who randomly appears in the ruins, and sings a beautiful mysterious tune (And yes, that is the girl from the preview people thought was from Team Magma. She isn't). She also has a Baltoy, and a Xatu.
Anyway, Kuruyo and her Baltoy are at the ruins because they hear that there is a precious treasure there, which she hopes to find and get more hope for her career. However, she has no idea what this treasure is. Afterwards, the woman appears and seems to know what the teasure is, but instead of telling them, she just hints.

Not sure about some in between stuff, but after much searching, the mysterious archaeologist lady with the Xatu and Baltoy reveals herself to be Kuruyo's "Mirai no Anata" meaning "Future Self". The mysterious portal in the ruins is a time machine, and she reveals to her that the "secret precious treasure" is time. Therefore, she learns that she doesn't have to rush things to be an archaeologist. In fact, seeing her future figure as one, she doesn't need any more hope!

Anyway, I'm not sure about the details, and I may have left some important stuff out, but I'll do a guide for this soon. I can't wait to see this one Also I guess this means that if she knows she'll someday get a Xatu in the future as well... and of course, her little Baltoy won't be evolving for a little while. Heh, what a way to lose hope.

Now, if only we got to see Ash's future self, and his friends... okay, I think I'll stop there to avoid flying fruit from the Shippers. =P

~Zak