To me, as I don't want to spoil people who aren't seeing the trailer, I am now more than confident to believe this.
I believe, that Luke is going to heel turn at the end of the film, and that is why we see Rey and Kylo talk to eachother, possibly after a saber fight that we saw in the trailer.
I think, if they played in the way that I think they are; Luke and Snoke will confront eachother, and that the both of them realize that Luke is not going at the Jedi Code, and that it's neither of the Sith. I think Snoke may use that to his advantage, influencing Luke to join him, and that he does accept it, as they both intend to change the Jedi's that were once seen in the beliefs and practices. This will cause both Rey and Kylo to abandon their masters, and alone; they realize that both of them have things in-common. Things that makes them realize that they have to confront their masters.
Yes, I believe Episode Nine will be the David vs Goliath for the Star Wars Universe, with Rey/Kylo as the davids, and Luke/Snoke as the goliaths.