And Secondly your are right the it can't replace fiat because fiat is a country's money which can be use as virtually and practically but bitcoin is internet currency and also international currency which can be use only virtually .
This is totally a way to get enter in the technology if the world or internet money .
Since the demand of the bitcoin is going increasing speedly with every second and Secondly after next halving no more bitcoin will produce then price will again more rise this will.make bitcoin more and more famouse .
So we can say it is only the future money .