I think ya, maybe it will be stable but if the currency has a very good value like gold for example, from ancient gold/dinar/dirham is very good if used as currency, because the price is very stable and no one can fake it.
I think it may be possible in very near future, because people have now started using bitcoin from all over the world having same currency with same value everywhere, and can use it without changing it into any other currency. Bitcoin can be consider as the future currency because we are expecting bitcoin to be use as a single currency throughout the world.