I'm going to say again what I said to tolbiny. Holders of dollars have no interest in taking any action that would make themselves poorer. The problems you mention in China is precisely why they will not flood the market with dollars. It would compound their problems. Everyone who holds $ has an incentive and a stake in keeping the game going. They aren't going to crash it.
China has already made the mistake of holding US dollars, they have no "good" way out. Of course they won't "crash" the dollar, but they will move out of it. Take their sovereign wealth fund they recently announced, it will be funded with 200 billion from their reserves. Their reserves are $US. Then they announced they are diversifying their reserves, more dollars on the market. The Saudis didn't follow the latest rate cuts with their own, Kuwait unpegged from the dollar to the basket of currencies and agreed to sell oil to the Japanese in Yen. Who is adding dollars to their reserves to counteract these measures? Just because the sell off is orderly and controlled doesn't mean it isn't a sell off.