I think the possibility of Finn being a Jedi is still very high. They never say he's not force sensitive and Maz, who is Force sensitive, gives Finn the lightsaber and then tells him to use it. I don't see why she would do that if he wasn't force sensitive. He is also shown to break the FO trooper programming, so he's not weak minded. He appears to do this when he has his "awakening" on Jakku, which is said to be a light side nexus, in the same way Dagobah, Malachor, and Morriband are dark side nexus'.
And I think grey Jedi is where this Trilogy is going. The concept of yin and yang, true balance between light and dark, and ultimately embracing the complete view of the force is the destiny for both Rey and Kylo. Even the Force Awakens novel opens with an excerpt from the Journal of the Whills.