Scotland, and NI. Which are 2/3 of the constituent "kingdoms" that were united to form the "United Kingdom".

Of course, it might not happen, but odds are rather better, in both cases, than they were pre Brexit.

Ninja Edit: This isn't to try and minimise the importance of Wales, just a recognition that at the time of the creation of the UK, the famous Encyclopaedia Britannica entry (For Wales, see England) wouldn't have been controversial in most of the UK. But even in Wales, Plaid have done very well, and become much more radical, as a result of Brexit.

I think the biggest question mark is whether Westminster will allow an independence referendum. I don't think they will no matter what the results in the coming election are. However if they do, recall that questions over whether we'd be admitted to the EU was one of the big issues that tipped the balance in favour of "No" - the fact that this is now a non-issue could be pretty huge coupled with the fact that many feel deceived over the issue.

I honestly think I will see a united Ireland and an independent Scotland within my lifetime.