From what I understand it, the proceeds of the sale of Mt. Gox coins would still go to their investors while the remaining coins would go to the owners after everyone has been paid off. Also, you can't just simply delete a wallet especially if people are still relying on that to recoup on their losses. The trustee who are handling the coins is just quite dumb to dump on exchanges, especially if there are loads of people willing to buy those coins OTC and they just need some facilitator to ensure that everything will work smoothly. Those coins were also one of the few reasons why there was a sudden dip in December after the price nearly reaches $20k.