It’s real in the sense that the established policy is to retire ccTLDs within five years of a country code ceasing to exist. But there are multiple provisos there:

• we don’t know with any certainty that the IO country code will be disestablished; it doesn’t necessarily follow that Mauritius regaining control of the British Indian Ocean Territory will mean the end of the IO country code (and associated .io ccTLD), for a variety of historical and administrative reasons
• we don’t know with any certainty that IANA will unequivocally shut down the domain, vs. converting it to a generic top level domain like many other existing special-interest and novelty gTLDs (e.g. .cloud, .gay, .info, .tech)

Obviously it’s worth keeping an eye on what IANA does with this situation, but personally I suspect one or the other of the above will happen. It’s probably in the interests of Mauritius to retain the domain as a source of income, but if they don’t then somebody else will likely want to take ownership, and there’s plenty of moneyed interests in retaining .io since a number of large business customers (the largest likely being Alphabet/Google) are already using it.