In their interview with Robert Downey Jr. for his new movie The Judge, they brought up the idea of him doing Iron Man 4 with Mel Gibson directing it:
DOWNEY: Yes, and I’m like, God, if I could find a part for Mel. But he also likes to do his own thing and sometimes he goes out of his way to do the unexpected. Sometimes with these things, it becomes a matter of time, and is seems like it’s getting a little bit old to hold a grudge.
DEADLINE: True, but the year he made Apocalypto, I didn’t see a better movie and he was ignored and hasn’t directed since. Marvel badly wants Iron Man 4 and you’ve said you aren’t doing it. How about the idea you’ll do that movie if Mel directs it?
DEADLINE: Is that our headline?
DOWNEY: Why not? That movie would be bananas.
Mel Gibson would certainly be an interesting choice to direct a Marvel movie as his stuff definitely doesn’t skew PG-13. But then again, both Shane Black and James Gunn were interesting choices that turned out very well in the end…