There is a zero percent chance of a one world currency in 2018, I'll offer anyone odds of 100 to 1 if they want to take it. It would take much time to transition to such a thing, it takes years to dissolve previous currencies and replace them with new ones, it would be even more extreme if it was happening world wide.
SDR already in use by central bankers all over the world, its been circulating and being used by government around the world for many years, all they need is catastrophic financial disaster probably index plunging 10000 point in one days and losing stockholders hundred of trillions of dollar to scare the people into surrendering their rights and freedom for more bankers control, thats when they say lets use SDR is the answer
They can makeup any reason to move to SDR, they can simply say we need new currency to avoid terrorist getting funds for their operation