Bottom line is that there should be no change if you've already satisfied residency rules, at least for short term, since the terms of residency don't include "must remain a citizen of an EU member state", those of us registered as "permanently resident" (living in whichever country continuously for more than 5 years) likely to face another "handling fee" for a new ID card conveying "EU Citizen" status as has already been proposed, those wishing to move AFTER Brexit may face a different process for residency depending on country of choice