I really think that there isn't a necessity to replace the dollar itself. I mean, we can certainly have all the currencies working very well, and if people have the right to choose what currency they want to use? Then no problem. What should be gone are governments forbiding their people to adapt Crypto-Currency. And let's face it, dollar is too strong and it will continue leading the world for quite some time.
Absolutely, even if we like to replace dollar but it seems very impossible, dollar has been existing and working well in our current system.
Bitcoin is just a small piece of payment system when compared to dollar, the government control this world, they have to do what is beneficial for all
and bitcoin is not.