Harrison Ford has revealed the fifth "Indiana Jones" movie is in the primary stages in a chat with MTV

MTV: Is a fifth "Indiana Jones" film inevitable?
Ford: I don't know. If we come up with a good idea ... Send
MTV: Is the ball in George Lucas' court at this point?
Ford: It is. That's the process. With some general input, he goes off and searches for the MacGuffin [Ed. note: That's the plot device that propels the story, i.e. the Ark] and then stumbles into a story. And at some point, we have a chance to take a look at it and give some input.
MTV: And he hasn't found the MacGuffin yet?
Ford: No, we're still in the primary stages.
MTV: The end of the last film leaves your character in a very intriguing position. He has a wife and a kid. Can he still be that man of adventure with those commitments?
Ford: And he's seen something. Remember those are the only witnesses to what he's seen. That's kind of interesting.
MTV: James Bond is a franchise that's figured out how to ably switch between actors. If, in 50 years, they find another man to play Indiana Jones, would that sit all right with you?
Ford: The very simple addition of numbers would make it clear that in 50 years I will not give a sh-- at all. I will so not care.
MTV: Well what if you knew today that someone else would wear the hat one day?
Ford: Fifty years from now, they can do anything they want.