~snip~
Bitcoin is a lot better than Fiat currencies because it can be used across borders and gives you complete control of your money. It has done well even with the decaying state of the global economy. If Bitcoin has reached this far, then it can do anything. I'd imagine people using it at a large scale worldwide pretty soon.
The pioneer cryptocurrency is not a "world currency", simply because it isn't officially recognized by mainstream governments as such. But technically, it is. After all, anyone can use it anywhere as long as there's access to the Internet. This is only the beginning of the "Bitcoin Revolution" that will change our world for the better. Who knows if someday BTC beats Fiat currencies for good? Just my thoughts

I don't think there's ever going to be a world in which we don't have fiat, and we only have Bitcoin.
The reality is that it's going to be much more complex than that. We will have Bitcoin living in parallel with fiat currencies.
Even right now there's some people living in a Bitcoin standard. They get paid in Bitcoin and they pay their goods and services with Bitcoin. Others have massive amounts of Bitcoin and they simply sell a portion of it every month to live off Bitcoin. On the other hand, there's plenty of people that live in a 100% fiat world and have no idea about Bitcoin.
Just like the Internet, the people that use the new technologies will get ahead, and the people stuck in the past will be worse off.