That would be interesting. From the trailer it looks as though she is lost and confused. I suspect that they may skirt the issue, but ultimately avoid it.
It would make for an interesting story, but with only 2 movies there isn't much time/space for her to fall to the dark side and come back to the light.
She doesn't have to come back to the light. She could become a Dark Side Jedi like Kylo Ren and Luke would be forced to kill her to save the Galaxy.
I actually like the sound of that, but it is admittedly quite dark for a movie that has a huge following among kids.
So was Episode 3, and it is considered the best of the Prequels by the majority. She can still be a Dark Side user and be really popular - like your favourite Darth Vader.
Besides it would appeal to all the Luke Skywalker fans to have their favourite save the galaxy instead of being killed off like Han Solo to make way for the new kids on the block.
I don't think they would ever choose to go down this route. If Rey turns to the dark side (and stays there) they obviously need a hero to rise up and defeat her. While I love the idea of Luke being the one to do so, Disney has to pass the baton off to the younger generation. They don't want to maintain the old guard as the primary protagonists of the series. So while I would enjoy such a story line, I think the probability of it happening is just about zero.
Which is why we get repeats of the same old story with minor twists and turns. Good job Disney. Perhaps they could introduce a new Force-Sensitive character halfway through who survived the second Jedi Purge and rises up to challenge the Dark Side Rey, but I suppose they are too spineless to do that as well. Why didn't they just follow the story of the Expanded Universe after RoTJ? Although I'm pleased that they brought in the Rogue One team instead of Kyle Katarn, because they are much better characters and their story is more believable. And they had Darth Vader slaughtering the rebels at the end.
The Force Awakens utilized a great deal of recycled elements from A New Hope, but we'll see what happens in The Last Jedi. I think Disney is very much doing a great job. Remember that they paid 4 billion dollars for Star Wars. It's only logical that they are going to play it a little safe at the onset. I know that you're not really a big fan of The Force Awakens, but it has been received pretty well, receiving much less backlash than the prequels did. Disney made a huge amount of profit, they've successfully rebooted the series and we have many more Star Wars movies to come. I'd say that ain't to shabby. I think its because they want to have the creative freedom to take the series in whatever direction the choose. The EU had a great deal of amazing content, but it also had a bunch of stinkers. Now Disney can choose to poach the elements they want and leave the rest behind. I still have my fingers crossed for a Darth Bane movie... even though I know it is unlikely to happen.
When does she finally find out that she has to put the lightsaber on the staff? Or the staff even IS a lightsaber? Dammit they set that up so well in the first movie, they just have to do it. Also rule of cool.
I want Kyle!!! Awesome guy. I felt that Finn corrowed a tiny bit of his background and I liked that - and hoped for more to be honest, that character had huge potential that was a bit wasted IMO. The story was told too quickly maybe.