The price of BTC is measured not in fiat ( $ ) but in stable coins - USDT,USDC…
There is an assumption which is most likely wrong that 1 USDT,USDC is always going to be 1 $ fiat.
To find why the assumption is most likely wrong please check this article -
The danger in the stable coins (thought experiments and the real price of Bitcoin)
The cental bank digital currency / CBDC on the other hand, like digital USD, or EUR, is not related to crypto-currencies like BTC.
So called digital USD/EUR will be direct replacements of fiat and guaranteed by central banks. A person holding digital fiat will most likely still need to exchange it to USDT,USDC…