Carcetti typecast will be tough for him to throw off, but it's doable. It's primarily an audience bias problem, but not exclusively, and great acting/writing/directing can overcome it. I think it's best to wait and see. I think it's something HBO knows how to defeat, and I expect the character to mold into non-Carcettiness just fine. It'll just take time. For example, I felt the scene where he told the story about The Hound was his first bit of non-Carcettiness