Understandably the expat situation (Brits abroad) and Eu citizens in the UK excercises us expats - often very heatedly on expat forums. The concensus is that May is understandably holding that card close to her chest.A mass relocation wouldn't serve either side. Don't be surprised if come the day of reckoning that no one has proper numbers of how many Brit expats there are in Europe. France for example actively discourages us registering- not necessary and just an overhead of paperwork. In Spain the situation is equally complex. A lot still live under the radar i.e. on a long holiday. At the other end of the scale are a small number who follow the rule books. In between lie a large number half registered as they see fit. So maybe in the health scheme here (as a dependent of a pensioner for example) but still paying tax (less) as a UK taxpayer on whatever incomes they have.
My guess is nothing will change for those abroad and registered for over five years as they are covered by (I think) the Vienna convention. Those with less than five years who knows. The big question mark is the availability of healthcare to the expat in the host country.
I have no doubt there will be a deal BUT have my suspicions that it will drag on for many years as more complex issues surface. In the meantime issues will be grandafthered i.e. continue as they are until the new thing is agreed. Here are just a few:
Customs inspections at Dover (remember the queues pre EU and that was much less commerce)
Irish /Uk border
Brit workers rights in foreign company in Uk/ Brit workers rights in foreign company in EU
The exit cost of £60Bn though I would counter that they could sell off (privatise) some of the infrastructure bought by Britains contributions so the net cost might actually be negative! The irony there is that is what the EU has been making Greece sell its family silver.
So long as both sides keep clear heads and act like adults then it should be achievable. I can't see that happening as the public will want to publically express their
outrage at every little detail and the press and social media won't be at all helpful. Sadly , unlike a divorce which can be worked out behind closed doors this will have to be visible and take account of protest groups.
On a lighter note, EU fishing fleet using UK waters? Well if you in Britain ate fish it might be a concern! However if it becomes an issue just use the Royal Navy. Our sparkly new carrier will be ready by then too.