Whether they introduce the CBDC or not, the blockchain technology has come to stay and they can only try but becoming a worthy competition isn't possible as their motive and that of blockchain isn't the same.
Why not? they're similar to stable coin, they can easily ban the usage of stable coin and force their citizen to use their CBDC. CBDC should be better in terms of regulation, while stable coin, there's no centralized entity will responsible if the stable coin get hacked or turn scam.
CBDC and Bitcoin are a different thing, they have no way to ban, but they can reduce their citizen to use Bitcoin by ban it.