I can't really reveal my source here, but I heard it from someone who works at Disney and was leaked something by someone else she knows who is working on some of the art for Episode IX. My friend was shown a photo on his phone of one of the storyboards for the movie. She didn't send me the photo, because he never actually gave her the photo. He just showed it to her, because Disney is trying to run a tight ship and anyone who leaks is under threat of being fired. Anyways, astonishingly the storyboard she describes is one Rey fighting Darth Vader. She wasn't quite sure whether time travel was involved to make this happen or if Kylo is actually dressing up as Vader or if it's a Vader force ghost or a dream sequence or what. But it looks just like the original Vader from the original trilogy, and she believes these story boards are going to be used in the film. So in some form, Rey and Vader are going to have a light saber duel. She described the setting of the fight as looking like it could be inside a space station of some kind, but she couldn't tell if it was the Death Star or what.
Anyways, that's all I know so far. Just want to put that out to you people to ponder.