It can't happen, because many reason such as:
1. Many people still don't really know about bitcoin or use bitcoin
2. Not every people can afford electronic device & internet connection to use bitcoin
3. Some people can't trust bitcoin as currency or prefer currency provided by government
4. Government can use various way to prevent bitcoin usage or adoption in their country such as ban/regulate bitcoin
5. Current bitcoin block size & network can't handle worldwide transaction (yet)
Nothing can monopolize something, but i believe bitcoin can dominate other currency in future.
really?
It can't happen, because many reason such as:
1. Many people still don't really know about bitcoin or use bitcoin
Time will tell everything, as time goes by i think people will know what actually bitcoin slowly.
2. Not every people can afford electronic device & internet connection to use bitcoin
not everyone yes but nowadays in 2016 almost 60% of 16-34 years old have a device & internet connection *from various sources at several research site, so it's not a big deal isn't it?
3. Some people can't trust bitcoin as currency or prefer currency provided by government
this is the main problem that i can see everywhere so far, people fear about bitcoin price movement that looks a commodity not as currency, don't know how to solve this