I've put together a kind of wishlist of stuff I hope they include in Star Wars Episode 8.
None of the Rey theories are correct. Most fans are speculating that Rey is the daughter of Luke or Obi-Wan's granddaughter. That's really quite limiting seeing how there's an entire galaxy full of force-sensitives she could be descended from. All the Jedi were killed, but there are other force-sensitives who were neither Jedi nor Sith. She could be anyone.
Force ghost Anakin. There's been a lot of speculation about how Anakin is probably desperately trying to turn Kylo back to the light side. Kylo probably stopped listening to him, or maybe Snoke fed him some lies to convince him to stop listening. Also, force ghosts are extremely useful for espionage purposes.
Princess General Leia. I want either Finn or Rey to not be sure whether Leia's proper title is princess or general, so they just called her Princess General.
Food issues. Finn and Rey are probably both going have some sort of eating disorder. As a result of his conditioning, Finn will likely eat any food offered to him in its entirety, but only eat that which is offered to him. Rey's probably going to have problems with portion control and hoarding. They're both probably going to be amazed by the fact that they can just come into the mess hall whenever they want and get a snack.
JediStormPilot. I've been around the block enough times to know that Rey and Finn are probably going to hook up. However, there's definitely some feelings between all three of our new heroes. It'd be much more interesting if they had a poly relationship. Of course, Disney would never approve that.
Poe calls Leia mom. That's it. That's the entire idea.
Leia's force-sensitivity. They only just scratched the surface with this in Force Awakens when she sensed Han's death. She doesn't seem much like a Jedi warrior, but she can probably at least defend herself. Though it would be cool if she had a green lightsaber in storage somewhere. If we don't at least see her stop a blaster bolt, I'll be disappointed.
Phasma gets more screentime. She had one or two scenes and then was promptly thrown into a trash compactor. At the very least, they could have shown her fighting the tentacle monster that probably lives down there.
Rey's lightsaber. Either she keeps using Anakin's or builds a double-ended one. If she builds one, it has to be double-ended. She's already got lots of experience with that fighting style, there's no way she would go with that option.
Inappropriate force usage. Including, but not limited to: flying, playing "keep away," stealing food, poking people, performing unnecessary upgrades to the Millennium Falcon, rearranging tools when Poe is attempting repairs to Black One, braiding people's hair when you think they aren't paying attention (Leia is totally paying attention), and "hey, watch this."
Give Rey a female friend. Leia's more of a mentor than a friend. I'm not sure if Jess is in this movie.