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.
We will still use fiat money even if bitcoin price reach $10000/
BTC1 obviously.
Because not all of citizens of the country using bitcoin and there are more places not accepted bitcoin for sure.
What may happen is bitcoiners use bitcoin more than fiat money and it's just an alternative of currency not a major.
Not everything can be purchase using bitcoin in the future.