You cant really kill fiat.
You can only limit its crippling printing press by switching over to bitcoin, but you still need it to pay bills since the world operates off fiat.
I dont think we will ever come to that point though since most of us will be either to old or buried by then to see it die.
Yes and I think that fiat will never die, there will be many users who will prefer to use fiat even if everything goes digital and they will be comfortable in using it.
Fiat is used by the governments to rob the citizens, so it will not be given up by the government. But bitcoin wil also be allowed.