I very much doubt that the .io TLD will vanish, too many big companies use it. Seen as non-country TLDs are allowed, I suspect that as soon as the country code goes away an existing registrar will buy it and .io domains will carry on.
The article is literally about how there is precedent for eliminating a country's TLD when that country no longer exists, in the .su and .yu domains (for USSR and Yugoslavia respectively).
It'll get eliminated as a country code, yes, but that leaves it available as a generic TLD. Seen as it will be available and is obviously lucrative, someone will register it and, presumably allow domains to be registered under it. Off the top of my head, I think it costs $10,000 and you have to show you have the infrastructure to support the TLD you register, so an existing registrar is the most likely. That figure is probably out of date, it's been many years since I checked it, but the infrastructure requirement is the more costly part anyway.
Sadly they will probably jack up the price while they are at it too. I just moved everything to my own petsonal .io a few years ago. I don't want to have to move again.