Brad Setser's analysis is that Americans have been repatriating their dollars even faster than foreigners have been getting rid of theirs:
"Words cannot really capture the sheer violence of the swings in private capital flows that somehow produced a a rise (net) private demand for US financial assets."
At some point, the balance of these cross-currents will change, and then? Maybe the turning point will come when Americans are forced to sell financial assets to meet living expenses and medical costs.
Meanwhile, Tim Iacono comments on a proposal to substitute the dollar as the world's reserve currency, with drawing rights from the IMF, i.e. a mixed bag of currencies. China's central bank seems terribly keen.
I have a sense of something being held up, but not for ever.