So only if the Orthodox reunite with the Romanists will they be allowed to call themselves Catholic?
That is already the case. There are 13 eastern rite Catholic churches. They are orthodox in liturgy and theology, but in full communion with the pope.
Personally, I consider the Orthodox equally entitled to claim apostolic succession with Roman Catholics. Many of my brethren don’t agree.
In addition, there are several churches that call themselves Catholic but are not in communion, and imho are not particularly Catholic. There is no inquisition anymore to keep these things straight. Kind of a pity, that.
They can call themselves whatever they want. So can the Calvinists and the Arminians, for that matter. It’s not as if the Catholic Church (Roman, FYI) gives out licenses granting who can be called what. It’s just according to our beliefs and traditions they are not truly part of the universal church.