Calzaghe is going take this by UD. He's too fast, too experienced, and on top of that the fight is in his hometown infront of tens of thousands of screaming fans. Kessler won't look completely outclassed by JC or anything, but I think he's going to be confused by Calzaghe akward, unorthodox style. I wouldn't be surprised to see Kessler do better than expected early on until JC figures out how to get inside and unleash a whirlwind of power-slapping.
As others have said, the real wildcards in this fight are Calzaghe's hands, if he breaks them early it could be a long night for him.