When bitcoin price hits 10,000$, Perhaps we will not use traditional currency (cash).
Untill that time, we will be using smart devices to pay everything with bitcoin.
Not all transactions can use bitcoin, especially related to the State transaction, as long as there has been no approval from the State, bitcoin will continue like this, that is used by the community only.
Fiat still exist and imposible be replaced, regardless of the price of the bitcoin will not much effect for fiat money, I continue still believe that the country will continue to maintain the fiat money.