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.
Thera are also ideas of tax avoidance and transaction fees to wory about.
A transaction alone with a transaction fee of around 0.0001BTC can take several hours to confim.
Take your cup of coffee at: £1.50 or ~BTC0.005
If you have a transaction fee of BTC0.005 it could still take half an hour to confirm.
Even when it is sent, if more people use it, there is more traffic so payments could bounce for several hours, days or even months before they are sent.