Believing in such thing as "unique" name is intriguing.
Also keep in mind that you're able to transfer a character with the name that you desire - So assuming that you're transfering your main toon, your main name will be saved. Unless someone tries to be a smartass thowards you and makes a level 80 with the name that you want. But remember that in order for someone to do that they're opening hand of one possible name that they own and want to troll you. So the situation is already being "countered" with the system that is going to be used.