Nobody really knows with the new vanity TLDs. They probably won't just disappear into thin air, but price hikes or other dark behaviours from their owners are possible. Delivering mail from them might be a bit harder too.

.io already raised their prices once it became the hip and cool TLD. .ai will likely see the same fate. On top of that there's the possibility that ccTLD's might impose restrictions on foreigners getting their domains.

I'd say go with the traditional ones like com/net/org, or your own country's ccTLD.