Heda You have to apply for EEA membership when joining the EU. But it doesn't mean you actually get to become a member, although I don't think that has happened before. A country only become a member after the existing EEA members all have ratified the new country joining. I think this is where the process currently is. Croatia has applied but not all EEA members have ratified this yet.
See this site: http://www.efta.int/Legal-Text/EEA-Agreement-1327 where it states:
"The latest enlargement of the EU took place on 1 July 2013 when the Republic of Croatia joined the Union, and upon the entry into force of the corresponding EEA Enlargement Agreement, the EEA will comprise 31 countries with more than 500 million citizens. The EEA Enlargement Agreement is provisionally applicable as of 12 April 2014 and is currently pending ratification by the Parties."
I don't know if that matters for bunq.