Yes, got you intrigued, didn't it?
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.
You're right that bitcoin can't replace fiat as we need fiat to buy bitcoin right now and every state have their own currency as official payment and become such as identity of the country. It's better to see that bitcoin as a mainstream payment in digital currency and has mutual support with fiat money. Each of them has it own advantages, I prefer to have both of them but bitcoin is more likely to get massive adoption in the future because many reasons : easier transaction to send/receive worldwide, low fees, fast payment as easy pay a cup of coffee with fiat (use your smartphone), high price and still continue to increase, the most important it's decentralized.