IMHO an alternative to the US dollar will come gradually. It has to be financially driven and not politically driven. As long as the US keeps printing dollars to paper over our deficit spending it is a matter of time nations may start creating an alternative on their own amongst themselves if the devalued dollar is causing inflation and killing them economically. Russia is threatening an alternative by using the Yuan, but China is not rushing into this without thorough review and calculations. China does not want Russia to drag them into a all out Cold War with the west where markets are no longer available and most of the GDP is spent on weapons. IMHO China rather have Russia/US/EU kill each other materially and financially in a Cold War. With the US and Russia drained by their fighting, China stands to gain in the Far East. IMHO China will remain with the dollar system as long as possible and will set up an alternate when the risk of a new system is less then keeping to the old system. The Russians are the only ones making noise about a Yuan alternative, but the Chinese officials have been tight lipped about it. IMHO if I were Putin I too would think things over before proceeding, especially when China is not saying a definite yes or no to the move.
I hope you are right. IMO, it will be gradual at first (we may be seeing the start of that now if you've been watching the index) and then it will happen "all at once (i.e., crash)".
The full FATCA implementation on 1 July may really start the snowball rolling downhill.
Again, I hope I'm wrong...