incorrect
If this aweful (!) thing should come to pass, producers will have excess euro's to sell, not excess dollars. No net effect on the dollar vs the euro, because the lower consumer demand for dollars is exactly offset by the lower producer supply of dollars.
moreover, if anyone wants to buy oil in euros or zlottys or cowpies, they can. find a seller who wants cowpies or a bank that will cowpies for dollars, and you are in business.