Fair dues, the Londonderry name is staying for now.
Sure we couldn't have the entire community calling it Derry or indeed everyone calling it Londonderry. If that madness happened how the heck could you figure out what type of human you were talking to?
What city are you from?
Answer 1: "I'm from Londonderry". Mmmh, clearly a Protestant/Unionist.
Answer 2: "I'm from Derry". Mmmh, clearly a Catholic/Nationalist.
Very useful indeed. We don't have many good tools like this in the Republic. It can take years to figure the religion or political slant of new acquaintances. :-)