Considering how little character devolpment Unalaq and Vaatu have had during this season, I think it would be a mistake to have them become the dark avatar and the ultimate villain of this season. I like the idea of dark avatar, I just don’t want it to manifest in that form. I have faith in these writers. I really respected them acknowledging how bratty Korra can be and throwing in the idea that her being more positive in life is going to improve the balance of the world. MY THEORY: Vatuu gets released, Unalaq pleads with him to enter his body. Vatuu decided its better to enter JINORA. I think this is why there has been so much set up for Jinora being so in tune with her spirituality. This will draw Vaatu to her. And the emotional weight will be incredible. Our heroes will be fighting for and against someone they deeply care for. You saw it here first folks!