Technically, all of them are required to join once their structural problems are solved - it's not that they chose not to adopt but rather that they were left out to avoid compromising the currency. Most of them have a clear political will to join the eurozone. The only real exception is Sweden, which effectively enjoys a de-facto opt-out like Denmark, for historical reasons (although they are increasingly under pressure to join).
Regardless, the hard core has won because the Euro is now a cornerstone of EU policies, whether the non-EZ countries like it or not. Every project, every accounting in the Union is now done in Euros.
> Technically, all of them are required to join once their structural problems are solved - it's not that they chose not to adopt
Denmark has a real opt-out. They chose not to adopt in a referendum.
> Most of them have a clear political will to join the eurozone.
No they absolutely don't have that. Even leaving out Sweden and Denmark - it's a toxic political issue in Czechia even though de facto euro is widely used in the business. And while Hungary has currently no chance to fulfill the technical conditions, there is also no political will to join until Orban is in power (and that will be a long time). The ruling party in Poland (PiS) is also explicitly against the euro, as is majority of the population.
> the hard core has won because the Euro is now a cornerstone of EU policies
The Euro won through merit - it just makes sense to use a common currency in the common market.
> Denmark has a real opt-out. They chose not to adopt in a referendum.
I know. My sentence was meant to highlight how Sweden is de-facto in a similar position, if not de-jure.
> it's a toxic political issue in Czechia even though de facto euro is widely used in the business.
Translation: it's happening no matter what.
Hungary and Poland are currently suffering from backwards political headwinds. In the past they would have happily joined (but couldn't). But again, like in Chzechia, it's basically happening de-facto no matter what. Once sanity prevails, governments typically find that having multi-currency systems is a headache.
