Yeah, but people say ‘Luke would never do that, the scene betrays his character!’ and I don’t agree with them.
I don’t disagree with the direction they took, but it could have been better handled.
What if Luke had looked into Kylo’s future and explicitly seen him kill Han? Then you have the man who couldn’t kill his evil father facing the man who will kill his heroic father (and led to the destruction of the Republic). If they had focused on that drama I think it would have improved both Han’s and Luke’s stories in this trilogy.
It’s a shame that they muddled that message by making Luke surprised that Han was gone.
I’m trying to imagine Yoda standing over a sleeping Luke in ESB, knowing full well in Luke’s rush to face Vader he could be turned and become a powerful enemy, and being so disturbed at the thought of his pupil joining his father on the Dark Side, he brandishes his lightsaber with the intention—no matter how fleeting—of murdering him.
Luke proved to himself and Vader in ROTJ that there is always hope. The idea that he’d even contemplate murdering a sleeping student who wasn’t yet guilty of any crime—knowing that the future is “always in motion”—doesn’t jibe. Even Luke reading Kylo’s thoughts while he sleeps is creepy.
What happened to Luke in the intervening years to turn him into someone who’d contemplate that? We don’t know, because the sequels don’t do a great job of showing us.
Edit: I just watched the scene again and I’m so annoyed at how Luke completely forgets everything he learned about internal conflict by saving his father and Rey spoon-feeds this wisdom to him like she’s the Jedi master. Ugh.