At some point, fiat currencies all over the world will suffer high devaluation, and we may see insane levels of instability. People will look for something better... but it will take time before they see that Bitcoin is the right way.
if this is happen, many government will trying to find better way for example with bitcoin so the government can use it to replace their currency. but i don't think that fiat currencies will have the high devaluation although possibility is always there. i think if we have bad situations like world war in every place then all fiat currencies will be interrupt.