Totally would never happen; it would require too many people to give up too much power. See also Brexit (the UK never fully integrated into the EU over this exact currency control issue).

I almost think the several countries that remain in the EU which choose to avoid or delay joining the Eurozone are better examples. While the UK evidently had other concerns with EU membership besides the Euro, even pro-EU governments seem to encounter opposition when it comes to the currency union.

https://en.wikipedia.org/wiki/Eurozone