It's yet to be seen if a fifth Indiana Jones film will happen. Ever since George Lucas announced his retirement I've written it off, but apparently everyone else is still interested in making one if Lucas decides to come up with a story. Karen Allen, who played Marion Ravenwood in the series, said she talked to Steven Spielberg about what she should say about Indiana Jones 5 if people asked her about it. Here's what she told Movies.com, when asked if she would do it,
I would! And I, in fact, just talked with Steven Spielberg recently—we e-mailed back and forth, and I said, 'What should I say? I'm doing this publicity, what should I say if people ask me that question?' And he said, 'It's in George's [Lucas] hands! I'm game, Harrison's game, and now it's up to George to write the script or to get the script organized, and the story.' And so I think it's—they want to do a fifth, from what I understand, but they don't want to do it just to do it, they want to do it if they can come up with a story that everybody is happy with and that everybody likes.
The last thing we heard about the possibility of a fifth film came from Frank Marshall who said the franchise was done,
I say, for me, [Kingdom of the Crystal Skull is] the last hurrah. I know that yes, we talk about it, but there's no idea, there's no MacGuffin... Yeah, no [George Lucas] isn't [hungry to do another Indiana Jones].
It's interesting that he said there was no idea because a few years ago, before this interview, Harrison Ford said,
The story for the new Indiana Jones is in the process of taking form. Steven Spielberg, George Lucas and myself [have] agreed on what the fifth adventure will concern, and George is actively at work. If the script is good, I'll be very happy to put the costume on again.
I doubt Lucas is actively working on it now. Who knows though, maybe he is and we just don't know it. Regardless, would you want to see another Indiana Jones film... if it was better than Kingdom of the Crystal Skull?