> In this case, though, would .io stay with the UK or come under Mauritian control? It’s not clear.
Before the retirement of .yu, Slovenia wanted to hold on to it, but it was not the successor state of Yugoslavia so they had to relinquish control and pass it to Serbia. So going by that logic, it would not stay in the UK (for long).
Mauritius could decide to incorporate it as "Mauritius Indian Ocean Territory", hence maintaining the CC. I expect .io owners will likely suggest something like that, while showing them how much money they could get from a 10-15% deal similar to what Tuvalu has for .tv. Nobody likes to burn money.