If the DAO hack gets laundered through XMR, it will establish a major precedent, and XMR will subsequently attract vast funds, as well as intense political pressure. Expect huge volatility, along with a massive long term upward price pressure in that case.
Personally, I would not choose XMR if I were the DAO hacker, except as a long term investment. I would move about half of my value into XMR cold storage, mix the rest as btc, and buy stolen gold and shelf-stable drugs on AlphaBay with BTC.
How would he move such vast amount of traceable coins to XMR?
Well, the question is was the hack actually illegal? - after all ETC stands by the idea that the contract is valid, there is no hack and ETH people reverted the transaction so should not care although could be interested in catching him.
How would he exchange the coins for any other coin exactly? What could the attacker actually do with the coins?
How much value does one tainted coin have vs untainted?
I say let the market decide! I think plenty of people would be interested in cheaper although tainted coins - just set the price right.