First point is that bitcoin is being used by every country their citizens just need an internet connection to take start with it, and it is true that bitcoin is not accepted by offline shops but you can easily use it online for shopping those things which you need for your offline life, and if bitcoin started to be accepted in offline life then I think the fiat will be converted by everyone to bitcoin in order to make it secure and to use t there.
That could happen. But it will take several decades for the bitcoin to be widely used in every country.
The Infrastructure for the digital coins are being built, in the mean time, the digital currency will become more popular.
Bitcoin has started to gain popularity now and we are seeing many more users who are getting into bitcoins, once bitcoin gets recognition at global level it will become more popular.