I guess it depends upon which country the passport is from and the relationship between the UK and that country. There is no EU passport as such, just a common format for EU countries. The EU is not like the US with a singular central government, it is just a union for trade and ease of commerce. In my opinion!
I imagine the EU and the UK have already ironed that out but I was unable to locate any info on the subject.
I guess it depends upon which country the passport is from and the relationship between the UK and that country. There is no EU passport as such, just a common format for EU countries. The EU is not like the US with a singular central government, it is just a union for trade and ease of commerce. In my opinion!
http://www.theweek.co.uk/brexit/73161/what-will-happen-to-eu-citizens-living-in-the-uk-after-brexit
I don't think anything significant will happen to them.
Nothing will happen to them.