bitcoin will never be able to suck all the fiat money, they can just print more without problem
also fiat is already worthless, but you're obligated to use it for the majority of things
if you mean collapsed, i don't think so
I don't agree with you that fiat money is worthless as every countries in the world are still depending on fiat money. Bitcoin and altcoin are still on the developing and it will take years for it to out smart fiat money and others momentary assets. We hope bitcoin price surge up to $10000 in a near by future, though bitcoin is currently fluctuations and we have a lot of uncertainty about its regulations.