Bitcoin is a very good thing to have as an asset. Just like gold. Even better if I may say. It's secure, and unlike fiat money it actually exists and work is put into it to produce it. This makes it great to store value.
However, it cannot and will not replace current fiat money that the entire world it using. It just cannot.
Take paying a cup of coffee for example. To pay your coffee with bitcoins, one must get bitcoins first, either by mining or buying bitcoins with other kinds of money (*cough*fiat*cough). It ends up being a quite complicated process, don't you think?
Until we reach the point where paying for a cup of coffee is as easy with Bitcoin as it is with cash, we will never get mass adoption. And as far as I see it, there is no way of simplifying the acquiring of bitcoins.
I think bitcoin can't really replace fiat. We all have different currencies in each country so I think it would be very hard for us to deal with changes in terms of finances. Also, most of the people around the globe don't have any idea and knowledge about bitcoin. Some people are doubtful about it too. I think fiat will still be fiat and no currency can change that as of now.