I totally believe that cryptocurrency can replace dollar in the future and there will be nobody wanna use dollar anymore 
. At the moment, there are few countries are going to legalize cryptocurrency as their local currency. Beside, as I know bank system at the moment is supporting for cryptocurrency by supporting for ICO project
I agree with you my friend, there is a high chance that cryptocurrency can replace the dollar in the future, because our world is going for the evaluation and we will use the new technology. Cryptocurrency is a good way for a lot of people to use their money easily without any problem and with a high security, but the first step is that bitcoin should be legalized at least at 90% of the countries in the whole world, then I am sure that bitcoin will be used more and it will be more popular so people will give up from using fiat and going for cryptos.. At the moment, there are few countries are going to legalize cryptocurrency as their local currency. Beside, as I know bank system at the moment is supporting for cryptocurrency by supporting for ICO project