People, you need a reality check. Most of you here are holding to a few BTC expecting to become millionaires some day. You are in a collective mass delusion - about 95% of you here.
Satoshi Nakamoto stated himself that with BTC there will be no middle way - it will absord the whole world's economy which is estimated to be around $100 trillion including the black markets. If this does not happen BTC will be literally worthless - not even half a cent that it started at.
The question of whether a new "universal" money will necessarily absorb everything, or will share its market with competitors, is an open one. There are arguments that go in the direction of a monopoly, but there are also arguments in the sense of a competitive market of different kinds of money (gold, fiat, altcoins, ...).
Nevertheless, I think you have the time scales wrong. It will probably take decades, if not centuries, to achieve the full conversion from the current fiat system to something else like bitcoin. It took more than a century to switch fully from gold to fiat (started out in the 19th century, where fiat was fully covered by gold and silver, and ended with the official release of any reference to gold with Nixon).
Even the bitcoin protocol wouldn't allow one to switch fully to bitcoin without an ecological disaster in the first 20 years or so, because the mining incentive would use up too much ressources (mainly energy and hardware).
Bitcoin is not just a technology such as the internet or the mobile phone. Money is much deeper rooted in society, and its adoption will be VERY LONG. So you cannot say anything about bitcoin's success before at least several decades.
I don't know how Satoshi saw that, but the fact that the inflation of bitcoin is programmed over 130 years, gives you an idea of the sort of time scale he had in mind. I wouldn't expect any monetary adoption to the mainstream before several decades.