I have a strong suspicion about the identity of Rey’s parents in the Star Wars Sequel Trilogy. I think they are Ezra Bridger and Sabine Wren from Star Wars Rebels. The reason for this is because they would be around the same age as Luke and Leia and throughout Star Wars Rebels there was an obvious connection between them. Ezra and Sabine may have gone their separate ways for now, but I believe that they will be reunited one day. Rey was born 15 years after the Battle of Yavin so if they are Rey’s parents they would each be about 34 or 35 when they conceived her.
As for their ultimate fate, because Ezra has used the dark side of the Force a number of times, I suspect that he will turn to the dark side and join the Knights of Ren and the First Order. On the other hand, Ezra may have tried to help Luke rebuild the Jedi Order but was killed when Kylo Ren destroyed Luke’s students. Sabine denied being Mandalore’s leader in the latest episode, but I think necessity will force her either to become Mandalore or become a close follower of the new Mandalore.
As to why they left Rey on Jakku, I think it is mainly Sabine’s doing. The reason for this is because she has recently been revealed to be a member of the Mandalorian aristocracy; her mother being a countess. In addition, since the Jedi and Mandalorians have fought one another for centuries there is bound to be ancient bad blood between them. Due to this, a majority of the Mandalorian clans may not like the fact that one of their own had an affair with a Jedi and produced a half-breed child. Sabine may have left Rey on Jakku to prevent her daughter from being targeted by the other Mandalorian clans. Also, if Ezra turned to the dark side and joined the Knights of Ren then Sabine may have also hid Rey to protect her from her dark side wielding father; similar to how Obi-Wan protected Luke on Tatooine. In general, Sabine would realize that her daughter would be surrounded by enemies and would be hunted all her life. Due to this, Sabine would have hid Rey in a backwater planet where none of her enemies would be able to find her.
I also believe that Ezra and Sabine will appear in either Episode VIII or IX. It has been revealed that new cast members include Benecio del Toro and Laura Dern. I think Benecio del Toro is going to be an older Ezra while Laura Dern is going to be an older version of Sabine. Both actors are the same age just as Ezra and Sabine are close in age and would be old enough to portray an older and wiser version of the characters.
I hope these predictions come true either in Episode VIII or IX. Only time will tell.