That's clear. Bitcoin can not replace the currency, in the world. Because, not everyone has the tools to use Bitcoin. As we know, Bitcoin need a internet connection.
Bitcoin doesn't need to replace any of the existing fiat currencies. It's mind boggling how people constantly keep focusing on this. Bitcoin is a perfect
alternative for those that aim to enjoy a high level of freedom, in form of not being dependent on any sort of central entity. For me Bitcoin is more like Gold, but then the 2.0 version. It offers an insane level of convenience and usability in terms of moving value from one place to another near instantly, and it allows you to store wealth outside the banking and governmental system. In terms of a proper all round currency, fiat is doing its job pretty well, and thus there is no point into changing anything in this regard. Bitcoin and fiat can perfectly co-exist, people for once need to stop being so short sighted.