I suspect a decision has already been made for Sweden to become a member of the EuroZone.
Because of the response of the Swedish Government to Nordea’s recent decision to relocate their headquarters to Finland, which has the Euro and is a member of the Banking Union.
From here it would be very easy for Sweden to quietly become a member 9in the same way as happened when she decided to become a member of the EEA..
Worth also considering that the UK and Sweden supported each other in resisting EU pressure to join the crowd and run over the cliff.
In addition, the EU with a single currency is not IMHO sustainable in the medium-term as there is no balancing mechanism to deal with the different rates of growth likely to occur when 27/28 economies grow at different rates. Basic economics any student would probably agree with.