If the Dollar is supplanted by IMF SDRs...

"we can get away with running a federal deficit that could hit $2 trillion this year only because of the dollar's status as global reserve currency. . . . the dollar would live on in an SDR-dominated world. It would no longer reign supreme, but neither would the yen or the euro or the yuan. Which might be the best long-run outcome the U.S. can hope for."

http://www.time.com/time/printout/0,8816,1890380,00.html