The UK might do as they please, and maybe they will. On the other hand, France, Germany or Italy need to sway the ECB or it's a no go. And if/when it happens, the other countries in the Euro will have to accept the resulting digital currency, which means let their citizen use it (or force them to, more likely). There is some pressure to do so. The ECB appears to hate bitcoin more than other central banks - see some of the papers published by a few ECB folks. A digital euro may help "solve the bitcoin problem". My opinion is that the USA (or the new president) won't care much or at all.