What happens if the Dollar ceases to be the international currency?

I am an electric engineering student, not much wise in economics, but there is a question that always bothered me, so here I have come to ask.Well.... most countries have dollar reserves so that they could maintain their exports/imports ratio favorable, But what if the the international community decides to replace the dollar for another currency (which is a natural tendency now days)? I mean, since most countries will not have to worry about the dollar value they could just empty their reserves, wouldn�t that result in the greatest inflation of history?