Episode VIII - New Female Lead

This could be an indicator that Rey and Finn are related to each other.

 

That's an interesting theory...

I remember the rumor that Luke was now evil, and that he would turn "Kira" made me very sad. If that happens in the actual movie I'll be heartbroken!

 

This would make for interesting story telling.

That said, I would consider this:

• Rey is a slightly bigger bet for a character in StarWars: it appears they are looking for a franchise female heroine, and her character being morally ambiguous could make achieving this goal problematic. (since previous heroines have all been supporting characters)
• For a mass audience, they've taken more incremental steps to showing someone being attracted to the dark side before being confronted with the "choice"... (Luke wearing black, choking Jabba's guards; Anakin using Padme as bait, and showing inability to control his rage).

I think showing Rey confronting the choice of going to the dark side could be interesting.

I also think that Kylo will be the one to tell the story of a "fall from grace" and be the mirror of Rey: he made the choice to pursue the dark side, and Rey didn't. And their futures are to show the outcome of those past decisions side-by-side. (Hinted by recent revelation that Kylo has a line in the movie “Is it true? You’re just a scavenger?” most certainly directed at Rey, almost mocking her current path)