Here's something from Boyega himself
Boyega on the Evolution of Finn:
You’re obviously part of a much larger plan for the franchise, so J.J. Abrams and Lawrence Kasdan must’ve had a lot mapped out before you even went in, but how collaborative was the process? How much were you able to contribute to Finn’s character as you went?
Boyega: They did have a lot of it mapped out. But the thing about mapping things out the way they do is they leave a very wide road that allows you to improv, to create your character. Obviously, various other people were going in for Finn and there were different versions of the same character. And they allowed that process to be organic. So, very collaborative … J.J. gives you ownership over your part and development of your part and for me, that’s something that is so important.
What were your instincts when approaching Finn as a character?
Boyega: I wanted to go back to the unlikely hero story that I do miss, like “The Warriors,” “Assault on Precinct 13.” The unlikely dudes that, when it starts the movie it’s like, “you won’t be anything but this.” And then they rise to something bigger, gradually, realistically. I love that. And that’s something that attracted me to this role.
http://variety.com/2015/film/news/st...lo-1201664002/
This is important I feel. Because so many people came away from this movie assuming that Finn is all he'll ever be at this point and Rey is the destined hero and "Luke" character
Just like Boyega said, the guy when people say "you won't be anything but this" but will rise to something bigger and greater, but at a realistic pace.
This makes it sound like Finn's journey is one meant for all 3 films.
And to go back to the Luke parallel... they both hit the main bad guy in the arm with one blow before the guy gets mad and then disarms/strikes them down essentially.
With Luke it was against Vader, even outmatched he got a hit in.. which made Vader start trying and dismember him.
Finn got his one hit in on Kylo Ren(the guy who wants to BE Vader and mirror his destiny) who was overconfident and Kylo responded, by disarming and striking him down.
That's quite a mirroring situation there too.
When Finn says "there's nothing special about me" makes me feel he's the guy meant for great things too.
Also to what Sacred said, she was so willing to let Finn have the Lightsaber, something tells me that she deep down inside essentially and eventually felt that he wasn't "ready" yet. He only became ready when he stood against Kylo Ren to protect Rey as well as himself. When he decided to no longer run and found something to fight for, that was the moment his journey truly started. He was struck down by Kylo Ren but because he got no 'closure' it seems like his journey is just beginning.
My mom actually has a theory, she said that she while she thinks Rey and Finn may wind up together, she thinks there's also a chance that Rey and Finn may wind up being brother and sister. Now as much as I want them to be a couple, her theory was that Abrams likes to mirror the other Star Wars movies, and in the first two films we're to assume that it's a love triangle between Luke, Leia and Han and some people pulling for Luke and Leia after the first movie.
But I asked her how it was possible. She said basically that there's many ways it could be done. But the most simple way is that after or during a falling out that Leia and Han Solo had, that she had an affair with Lando. Which is essentially what hurt their friendship as well as drove the deeper wedge of 'regret' between him and Leia. Which would make sense, because if Finn is indeed the son of Leia and Lando, he still is a Skywalker by blood. Which would answer why he'd be a force sensitive that wasn't thought to be a Skywalker.
THOUGH she feels it's more powerful if there's a force user that is not a Skywalker and loves the humble beginnings Finn starts from, they still have enough to go that route if they chose to.
I find that a very interesting theory, both of them actually.
Personally, I'd love for Finn and Rey to end the series together and in love. But I can't deny both theories hold possibilities.
He of course could also be the son of Sana Solo/Starros
But that is less likely as only the comic readers would know of her, unless she appeared in Rogue One. Though she'll likely be in the Han Solo movie. So fans may know of her by then, so who knows.
So many wonderful directions to go with Finn and how great his destiny could be, that's what makes him such a great character to speculate about.
My two cents? He'll be in a coma for most of Episode VIII and will probably be going through a journey in his mind with The Force calling out to him and we'll see flashes, journey and steps, but as I said, I think Rey will turn to the dark side, and he will sense it, and that is what will wake him up. When he wakes up either Maz, Luke or Kylo Ren will be staring at him, make a reference of journey or the work they have to do, and the movie will end.