Speculation…
Shmi “There was no father. I carried him, I gave birth, I raised him. I can’t explain what happened.”
Palpatine using abilities “some consider to be unnatural” conjured this child of the force within Shmi (a random slave of no importance). Palpatine is secretly Anakin Skywalker’s father (and acts like it throughout the PT).
Palpatine - having survived his fall down the Death Star chasm (much like Luke survived the Cloud City chasm - it rhymes!) used those same abilities to create Rey, again within a random junker of no importance. Palpatine is Rey father, she’s of the same line.
Seems at least possible?
Rey would have only been conceived a decade or so after the Battle of Endor. I think it’s more likely that Palpatine won’t literally appear but rather that our heroes will be dealing with some kind of contingency plan he set up before he died. After all, the books and comics have been dropping breadcrumbs to that effect since Shattered Empire and the Aftermath trilogy.
Anyway, I hate the title and I’m more confused by the trailer than anything. JJ’s doing his old gleefully cryptic schtick again, and I feel like I still just don’t have enough to go on to make any kind of judgement beyond “nice to see Billy Dee flying the Falcon again” or “Finn’s new costume is cool”. Would it kill Abrams/Kennedy to have given a three-sentence summary at the panel so that I could have some vague idea of what the stakes are here?