Mad Max 4 is still is the earliest stages of development, but there are some new casting rumors that are worth paying attention to. Most notably, Mel Gibson is not expected to return to his iconic role. From E Online:
The Mad Max revamp is a long way from fruition, and Miller is being very secretive about the roles and plot. Actors auditioning for the film have only been given a letter for their character's name. The studio has yet to sign off on Miller's choices, and no formal offers have been made.
Although Mel Gibson went off the deep end of crazy a while ago, he seems to be fixing himself up. It would be nice to see him play the character again.