It would have no positive or negative impact on bitcoin adoption. CBDC(Central Bank Digital Currency) is just a digital form of a fiat currency.
          Actually traditional banking authorities have continuously failed in competing with the gradual growth of crypto currencies adoption globally.People mostly prefer Cryptos due to their decentralized nature and easy usage.
          So in order to make their fiat currencies to be used more, they have decided to release CBDC.
           China has recently checked its yen in digital form in some cities and now it's Japan's turn.