Becoming a world currency that's a huge one. There are certain factors to be considered before flagging off a currency. The Government can't flag off what they don't have control over it. Now bitcoin is decentralized but cannot be traced. Don't get me wrong, your transactions are visible but a name and a face is not attached to it. So chances of using it for fraud are on the high side and if that cannot be controlled then it can't become the world currency. But widespread adoption is going to happen because it solves the need of remittance.