I'm in agreement.
Why do I think this? Luke's theme song plays when the bad black suited dude with the red light saber appears.
Could Luke have gone over to the dark side? I hope so. Would be incredible storytelling. What would have caused him to turn?
Or even darker still - Luke is killed in this one.
If it is Luke, then when he says I'll finish what you started, talking to the destroyed helmet of Darth Vader, he could mean finish destroying the Empire since it was Darth Vader that killed the Emperor.