Bitcoin NEVER will be defacto currency of the world. Bitcoin is plagued with people who just seeks profits using power hungry miners, if bitcoin were to change to Proof of stake, THAT would be defacto currency, but its not happening as miners who have to suicide voting for a BIP like that, so Bitcoin is doomed to fail in the end. Now, by other hand, ethereum has PoS future and is well known as bitcoin, i am positive that ethereum will take over the world