I can’t see that that would happen. Reversing the Brexit decision comes in different flavours, but none of them lead to adopting the Euro. Let’s say that Parliament refuses to approve the triggering of Article 50, or that there’s another referendum and the majority of people vote to stay in this time. Now, both of those scenarios are highly unlikely and I can’t see them happening at all, but even if either of them did take place, I don’t believe that there’d be any appetite for then pushing the UK further to more cooperation with the EU.
At the furthest extreme, you’d see Remainers campaigning to return to the status quo, to how things were on the 22nd June this year. I think there’s no appetite for the UK to join the Euro and the EU isn’t in a position to require the UK to join because the UK has an explicit opt-out. The prospect of joining the Euro was kicked into the long grass by Tony Blair and Gordon Brown, and there’s no politician who wants to return to it in any form. So much would have to change in so many ways that it’s not really a conceivable set of circumstances.