OPEC has already adjusted to the falling Dollar (seen oil prices recently?!).
China and India both want the Dollar to be high, that's why they are hoarding Dollars. India alone holds more than $110 Billion in U.S. currency.
What you are failing to accept is that foreign governments such as China and India are intervening in the market; i.e. the market is no longer a free trading market. What we have going on is international currency manipulation on a large scale.
This manipulation makes the price of imports into the U.S. artificially low. It is a stealth subsidy of Indian and Chinese industry.
To counter this de facto subsidy, our Fed is letting the Dollar fall back towards what would normally be its true free market value. This will take some amount of time, and yes, the currency holdings of India and China will drop dramatically in value. They seem willing to risk such an investment strategy, however, probably in the hopes that the U.S. will change Administrations to someone who lets them play their currency manipulation game a little longer at the expense of American jobs in the meantime.