I have just read in the book the part where Kylo Ren interrogates Poe Dameron to learn the location of the map leading to Luke Skywalker. During the exchange Kylo criticizes Poe for revealing himself by shooting at him as a way to get back at him for killing Lor San Tekka. Kylo says that revenge is childish, that it accomplishes nothing. It is a small thing to say, but it got me thinking. This is a very un-Sith like thing to say, and then I was reminded that Kylo is no Sith at all, not only that, but he seems to have been taught against the Sith ways (presumably by Snoke).
The main theories about the identity of Supreme Leader Snoke are that he is of Sith origins whether it be Darth Plagueis, Sidious, Vader, or an unknown Sith lord. This reading has got me thinking that Snoke is probably not a Sith at all, or at least not anymore. Snoke has taught Kylo (and probably the Knights of Ren) that revenge is useless. They are also hunting down the last of the Jedi, Kylo speaks to Vader's mask saying that he will "finish what you started," and I believe he is referring to wiping out the rest of the Jedi. I believe Snoke (and probably Kylo) are convinced that the fall of the Republic, and the Empire, are due to the Force groups' actions, both the Sith and the Jedi. They are attempting to wipe out the Jedi so that they can establish a "new order." Not a Force order that is of the Light Side, or even the Dark, but somewhere in the middle. The Knights of Ren and the First Order are not doing bad things to be bad like the Emperor, or doing the right thing to ease their conscious-es, it is about doing whatever is necessary to maintain order on the galaxy. Sometimes it is about killing jedi, sometimes it is about not letting sentiment cloud your judgement.
I cannot recall where but I can recall an interview that revealed that Kylo was not a Sith, but that he is a Darth Vader fanboy. He is not trying to be a Sith, he is trying to be his grandfather, which explains his mask and his lightsaber. In the original trilogy Vader was not like the Sith lords that we learned about in later years, he was simply an enforcer of order for the Empire. He is not remembered for his extraordinary Force powers or lightsaber dueling skills, he is remembered for his ruthfulness and cunning to defeat the Rebellion. Vader captured Leia, put a tracking device on the Falcon which leads the Death Star to the Rebel base. In Empire he knew that the Rebel base was on Hoth, he set up the trap to freeze Luke in carbonite. His lightsaber is not red because he is Dark Side, its red because Vader's was red. He has the mask and voice changer because that's what Vader had. Kylo is constantly being pulled towards the Light Side, that's not the problem, (his parents are Han and Leia for crying out loud) the problem is that deep inside he is not a bad guy, no matter how much he tries to be Vader. To convince Snoke (but mostly himself) that he can embrace the Dark Side, he kills his father, and the movie's novel illustrates how terrible and conflicted Kylo is after killing Han.
So how will this effect Episode VIII? I think that Episode VIII will show just how complicated this new war is, that everything is not simply black and white, but many shades of gray (that saying is just tainted forever isn't it? :p). I think this will reflect how the world is today, that there is no good and evil, moral and immoral. Gone are the days of right and wrong and a new form of good has arisen, which is acceptance of everyone. But enough about that.
So my predictions about Episode VIII? Kylo Ren will try to become more attuned with the Dark Side but will fail to do so. Rey will be persuaded to join Snoke. Luke will defend the jedi order and probably die doing so. Snoke's identity will be revealed as someone who is not a Sith (I am still leaning towards Plagueis, after he has seen how flawed the Sith ways are).