"Harrison Ford told France's Le Figaro (via People) that 'the story for the new Indiana Jones is in the process of taking form. Steven Spielberg, George Lucas and myself are 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.'
The fourth film, Indiana Jones and the Kingdom of the Crystal Skull, was released on May 28, 2008 and earned $786.6 million worldwide. It was made for about $185 million."