Bitcoins had becomed the main coin in digital currency all of the alternative coins be traded with bitcoins, I think what do you mean with main coin is bitcoins become main currency, the fiat money will be replaced by digital currency bitcoins and fiat money will be useless. It will apply to all of fiat money around the world, it is hopefully of community bitcoins become main currency in the world due to the system of fiat money is broke, it can not be against the crisis of economy.