I think it is impossible to replace with conventional money, even the government alone is not possible to allow it.
Our governments can never allow this to happen that is why in some countries bitcoin has not be legalized because the see bitcoin
as a threat which can replace conventional money and lead to the collapse of the systems used to regulate cash flows.
to me when our people will put pressure on our government by using bitcoin in a large scale they will defiantly start thinking about bitcoin and will try to legalize bitcoin.