Apparently Gibson turned the job down, but Downey has found a replacement. He's now released a video online saying he'll only do Iron Man 4 if notorious radio personality and X Factor judge Howard Stern directs.
See the video below:
Of course, that video does appear to have been filmed in Stern's studio. In other words, don't get your hopes up fans, we're pretty sure Downey is just messing with you now.
Downey will return as Iron Man in Avengers: Age of Ultron, opening May 1, 2015.