There have been many theories about what happened to Luke Skywalker in his final moments in Star Wars: The Last Jedi, but it was clear that Luke was dead, having sacrificed himself to help the Resistance escape. Of course, death is never the end for the Jedi, but that detail was hardly conclusive evidence that Hamill would be back. It was also entirely possible that Lucasfilm could have tried to make Luke's return in Star Wars Episode IX a surprise by leaving him off the cast list, but instead, they've made it clear we will see Luke again.