Everyone has their one opinion on bitcoin, if you say BTC will not be the world currency in the world then no will argue with you because that is how you see or your point of view. Bitcoin did not come to remove Fiat currency but bitcoin is here to strengthen the Fiat currencies in the world if only they understand the coin adopt it.
What you mean by bitcoin is here to strengthen the fiat currencies in the world if only they understand the coin and adopt it? In my opinion and opinion varies, Bitcoin is not here to become a world currency neither is it here to strengthen fiat currencies. Why would it want to strengthen fiat currency? Bitcoin has come to be a great alternative to the fiat currencies and the present financial system and not to strengthen it.
Think about it, if it was here to strengthen and support the present traditional financial fiat system of payment, then governments of the world would love bitcoin and support it.