If Hamilton leaves it will be a boneheaded move of the same magnitude as Thabeet.
Why was Thabeet leaving a boneheaded move? He had just gone to a final four, the team was graduating its PG, backup PG, and PF. Also he was #2 overall. Thabeets biggest mistake was not getting better and being drafted to a team with Marc Gasoline on it.
Hamilton is a different story. He would be returning to a team that had a poor season, where his stock isn't extremely high, and is returning most it's players. However, he also knows from his brother how hard it is to stick in the NBA. It would be somewhat shocking if he chose to leave for the NBA. I could see him transferring, but only if he could get a waiver to play immediately.