I agree with #3 and I imagine Brexit will be reversed because of demographics. Give it a generation or so and the conformist younger people who have had globalisation propaganda and lack of pride in their country programmed into their minds since childhood will vote to rejoin. Every TV show, every teacher, most NGOs, are at it.
Got it, people only ever want to join a bigger federation of states due to brainwashing and lack of pride in their own state. Good to know you have all the answers.