"I finish Episode VIII, and then I'm out of work," Hamill said when asked about his future with the franchise during a conversation with Ray Davies of the Kinks, in a report from Den of Geek.
Most likely, Hamill's not spoiling anything about the next two episodic films in the Star Wars franchise. More probably, Hamill was speaking of his immediate plans, saying he didn't have anything directly on his schedule after wrapping Episode VIII.
Hamill loves to tease, but has never let out an outright spoiler, and it's not likely he started now. Still, reports of the final sequence being shot had only Daisy Ridley (Rey), Mark Hamill (Luke Skywalker), and Adam Driver (Kylo Ren) present in Ireland at the real-life location of the fictional First Jedi Temple. That is the kind of showdown that could result in a death.