So I'm thinking the plot goes something like this:
1- Luke has been away for 30 years.
2- Lea/Han/Rebels/good guys are in a dire situation due to some new threat or resurgence of the empire, whatever
3- Lea/Han's son, wanting to save them, goes out on his own looking for something/someone to turn things around.
4- This is felt as an "awakening" of the dark side, felt by Luke, which "awakens" Luke. Cue the awakening of both the dark and light side.
I'm guessing the cloaked figure is Solo's son and he has his grandad's sabre which he "fixed". The sabre's chaotic appearance symbolizes his attempt at rebuilding something he doesn't quite understands; he doesn't have good control of the force and it shows in how he built the sabre into something unique but somewhat dysfunctional and chaotic.