I don't believe Bitcoin will be what replaces paper money and electronic government debt. I'm not even convinced that Bitcoin will be the survivor in the crypto coin wars. Most initial iterations of software are not the final useful form that becomes popular.

Something will eventually replace fiat maybe even in our lifetimes. I always figured it would be some form of ID at birth that can follow you around all your life. Maybe DNA account assignment or fingerprint/retina scanning. People can be assigned government credits by employers and deduct against them for things they want to buy. This would have the side benefit of eliminating many types of crime that revolve around untraceable currency.