[Oling_Roachinen]

Spoiler!

I think Rey's just going to end up being able to use both sides of the force while remaining good and the red double bladed lightsabre will be a visualization of that.

Unfortunately, I do think that they might be limited by Disney of making Rey evil just given the whole using her to sell to millions of young girls. Although another case of Daenerys going genocidal-crazy would be funny for the parents who ended up naming their kid Rey.