That Bitcoin, or a similar currency, would be able to replace different global currencies because it is a thriving-new economy that is able to run and operate from any computer with Internet access and many banks and currencies have already made there way online so I think that Bitcoin could easily replace different global currencies.
Bitcoin is completely virtual and with no federal government backing it. The value swings tremendously from moment to moment, and the fluctuations are scary for those who want to invest in it. You need something more sturdy to be a global currency. It will never reach the status of the US Dollar, Pound, or Euro
No, Bitcoin will never replace any global currency, because it is a broken system in itself. It is only a matter of time as computer gain more processing power and people can start to generate their own Bitcoins out of digital air. Plus with the unreliability in Bitcoins strength as a currency, it would make no since for a global currency to make the switch. Bitcoin is not stable and valued could be equal to a thousand dollars in the morning and by evening could be only eight hundred dollars. A currency doesn't want to have that kind of value shift so quickly.
I do not think Bitcoin will replace different global currencies. I will admit that I do not fully understand the mechanics of Bitcoin, or any other cryptocurenncy for that matter. However, I do not think that it will replace other global currencies because I feel like physical money will always be needed.
The idea that Bitcoin could replace all national currencies is very presumptuous. Would it make sense? Sure. However, nations are run by people. People have pride. Pride is not sensible or logical. Nations will hold on to their currency just for the sake of it. Even the Euro is having trouble maintaining itself in the European market.