I have studied and argue about Bitcoin some topics which I posted and also came across in other board. Today I begin to think about the whole Idea of Decentralization, and I think the inventors of bitcoins since the idea was conceived till it was birthed has done the greatest good to humanity. With my view as at the time of writing , I think bitcoins will go long way to reduce poverty if they allow it achieve it's purpose. Reducing poverty in my context is not about profit but the peer to peer transaction mechanism. The idea of centralized exchange is very much in place because a lot of people are yet to accept bitcoins but once it become accepted by majority, I think there will definitely be no reason to convert to fiat.
You make an analogy with a slightly different context in my opinion, because if the majority of people in this world are willing to accept Bitcoin for many things and for many payments, of course there will be fewer fiat users. This will also happen if everyone in all corners of the world already knows Bitcoin and uses it, because if there are still some of the world's population who don't know Bitcoin. Of course the use of fiat will continue and continue as usual and fiat will not just disappear in all circles of society.