I don't understand why anyone would believe that. The euro does exist since only a quarter of a century and is already in very serious dire straits. It's the worse ever conceived currency (conceived by clueless bureaucrats): it makes no sense at all to have a common currency for countries with different fiscal policies. Nearly all the countries that have the euro are more indebted than the US (GDP wise). One country with the euro already partially defaulted on its public debt (Greece).