It's no mystery by now that Luke Skywalker had chosen to banish himself after the fall of his new Jedi Academy, but as it turns out, part of Luke's guilt was his failure to foresee the betrayal of Ben Solo. Apparently, Luke had thought that Ben was the chosen one before it was all too late.
In an interview with Entertainment Weekly, Hamill explains:
"[Luke] made a huge mistake in thinking that his nephew was the chosen one, so he invested everything he had in Kylo, much like Obi-Wan did with my character, and he is betrayed, with tragic consequences. Luke feels responsible for that. That's the primary obstacle he has to rejoining the world and his place in the Jedi hierarchy, you know? It's that guilt, that feeling that it's his fault, that he didn't detect the darkness in him until it was too late."
For now, it looks like Kylo Ren has followed the same footsteps as his grandfather, being considered the chosen one and having a strong connection with the Force. If you look at it technically, Anakin was still the one who killed the Emperor himself, thus fulfilling the prophecy, so calling him the chosen one isn't wrong.
To be honest, I think the "chosen one" moniker is a bit too cheesy, even for a universe like Star Wars. I don't know where The Last Jedi is taking the story, but I think it would be cool if we just watch Rey fight evil because she chooses to and not because it's her manifest destiny.
That's just my own idea anyway.
Catch Star Wars: The Last Jedi in theaters Dec. 15.