Another cassanata is inevitable given his past, and if I were defending against him, I would know exactly how to make him lose it.
However, at this stage in his career, I believe he is smart enough to realize that a move to Juve would be the last time a big club are willing to gamble on him. Factor in azzurri ambitions, and I think he would control himself.
Even than, nobody needs to control him, just guide him. I think part of his brilliance as a footballer is directly related to these shortcomings in his personality. Maybe it's just a romantic idea, but I can't help but think that Cassano wouldn't be so bold on the pitch if not for his temperament in general.