According to this chat with Peter Jackson and Guillermo del Toro, they have "plans" for Ron Perlman in the Hobbit movie(s).
So speculate away! He'd make a decent King of Mirkwood, but only if David Bowie is unavailable. Or better yet, Beorn, if Beorn doesn't get cut out of the script (with two movies and del Toro's penchant for crazy-odd shit, I can't see them cutting a shapeshifter out).
