"These coins will be part of the money supply. It's the same money, just not a dollar bill with a serial number on it, but a token that sits on this blockchain." according to some source.
The first thing that came into my mind is whether the new digital currency will be as "free" as Bitcoin, "free" as in the anonymity of using it.
Central banks would want control over the digital currency. However, are they going to spin up mining farms which consume enourmous amount of electricity to power the blockchain of the new digital currency? Or will the public be allowed to mine the digital national currency? I doubt that. They would save gigawatts of electricity per day if they opt for a centralized system where the central banks will verify and sign each transaction and only publish the public ledger. Besides, by doing so, they can maintain the control of money supply and once people fully convert from paper money to digital cash, they could track our monetary transaction down to every single cent.
But this is not Bitcoin anymore. The core of Bitcoin is the block chain which is kept and updated by decentralized miners in a peer-to-peer network.
We do not know what will happen to Bitcoin, but lets hope that Bitcoin will remain as "free" as it is and continue to become a strong alternative for value transfer and value storage.