We have seen that the biggest exchanges for ETC and ETH have frozen funds of the white hat hackers to stop their plan to dump their coins. So I think they will do the same once the ETC of the DAO attacker moves in Poloniex and Kraken too. They will not allow to be used by the attacker as a playground for their bad motives. I do not know what the smaller exchanges will do.
That would be good. But for the DAO hacker, he can just do it off change or mix the coins. Is there a way to prevent that?