I mean, the .su TLD which was for the USSR, still exists, and still taking registrations, so I don't think a region stopping existing as far as ISO country code

I mean, the .su TLD which was for the USSR, still exists, and still taking registrations, so I don't think a region stopping existing as far as ISO country codes are concerned, is always going to be fatal - Mauritius I imagine could petition ICANN to keep it alive (and make some revenue from it)