Fiat will not be worthless and the simple reason for that is on the basis that its something that have been with us for long and humans over the years with the slow process of adaption have come to make it part of our life anything that wants to come in form of currency will only compete for space and nothing else... Another reason again is the fact that Fiat is not universal across the world this important factor will not make it easy to be abolished as different societies attach different sentiments to their currency...