I learnt of this while reading Manuel Moreale's Peoples and Blogs conversation with Ben Werdmuller:

At some point, I’ll need to change my domain name. Werd.io is part of the .io top-level domain, which is assigned to the British Indian Ocean Territory. Quite rightly, and far too late, the British are ceding that territory back to Mauritius. At that point, there will be no British Indian Ocean Territory, and by ICANN’s rules .io will stop being supported.