Warning: Possible spoilers for Star Wars: Episode VIII follow.
We get some potential insights as to the origins of the Jedi as well as Rey from a rumored Star Wars: Episode VIII script(?) leak featuring a scene and dialogue between Luke and Rey.
The scene seems to indicate that Luke takes Rey on some sort of Force vision journey (à la Force Awakens' Maz Katana) where the origins of the Jedi are revealed.
If legit, it says that Anakin Skywalker is not the Chosen One, but that this girl is actually "The One" (sounds a lot like The Matrix).
The info says that a brother and sister discover a tree which gives them Force powers. The brother ends up killing the girl and their mother and father. He then gets transformed into what sounds like the first Dark Side/first Sith. The girl then gets transformed into the Light side.
It's then said that the girl ("The One") trains locals as being the first Jedi Order, and that one day she will return as "The One" -- either as a boy or a girl -- to bring balance to The Force.
Luke then explains that the Jedi got it wrong about Anakin being The One, which led to the earlier Star Wars movies and Vader.
We can speculate that Rey is "The One," and that the tree may be located on Ahch-To, the planet at the end of Force Awakens where Rey meets Luke.
Read it for yourself below (click to enlarge).
"Star Wars: Episode VIII" has a December 16, 2017 release directed by Rian Johnson starring Mark Hamill, Carrie Fisher, Adam Driver, Daisy Ridley, John Boyega, Oscar Isaac, Lupita Nyong’o, Domhnall Gleeson, Anthony Daniels, Gwendoline Christie, Andy Serkis, Benicio Del Toro, Laura Dern and Kelly Marie Tran.
Star Wars: Episode VIII announcement teaser: