Shane Black will be in charge of the third installment of the Robert Downey Jr. starring franchise. Black has only directed one film, Kiss Kiss Bang Bang. But here's where the information gets interesting, he may write the movie as well. As far as writing credits, Black has a ton. Those films include the Lethal Weapon films, The Last Boy Scout, and The Long Kiss Goodnight. Funny thing about those films is, they're all action films. This will work really well for Black when it comes to Iron Man.
I think he's a good choice for the script, I don't think he's the man to direct. I think it will be nearly impossible for anyone to fill Favreau's shoes. This is his baby, as much as Marvel doesn't think so. He created the world that Iron Man inhabits and he got the Avengers movement going. We'll see how long Black works with Marvel before they ruin that relationship too.