In the original Star Wars trilogy, Luke Skywalker was in his late teens/early twenties. If rumors are to believed, then Star Wars Episodes 7, 8, and 9 will feature a Luke Skywalker that is in his late thirties/early forties. Since Mark Hamill is now 61 years old, it would be a little bit of a stretch for him to play someone in their thirties or forties.
Of course, it's only a rumor that Luke Skywalker will be in his thirties or forties, coming from someone who wrote an unauthorized biography on George Lucas and claims to have seen twelve story outlines for Star Wars films. It's entirely possible that George Lucas might have completely changed his mind since the time those original story outlines were written.
Given the fact that Mark Hamill claims George Lucas invited him and Carrie Fisher to lunch to tell them that he planned to do Star Wars Episodes 7, 8, and 9, it's probably not that farfetched that George Lucas was thinking about including them in some form or fashion. Now, it's highly likely that Lucas might have just envisoned them in cameo roles or was just letting them know as a courtesy, but it's also possible that he wanted them to reprise their roles as the main characters.
While both Mark Hamill and Carrie Fisher have remained active in Hollywood through the years, neither has managed to match the success that they had with the original Star Wars trilogy. Would Disney be willing to take a chance on putting them in leading roles in what will surely be a big budget action movie?
Even though most would probably think not, it should also be remembered that Harrison Ford played Han Solo. While Mark Hamill and Carrie Fisher's careers might have stalled after Star Wars, Harrison Ford went on to star in a number of other blockbuster movies. Even though Harrison Ford is now 70 years old, it was only four years ago that he reprised his role as Indiana Jones.
Having Harrison Ford reprise his role as Han Solo could be a major box office draw for Disney. In fact, it would probably be difficult for fans who grew up on Star Wars in the seventies and eighties to imagine anyone else in the role. And if Disney were to go with a 70 year old Han Solo, then a 61 year old Luke Skywalker and 56 year old Princess Leia would make sense. What do you think? Should Disney bring back the original Star Wars cast for Star Wars Episode 7?