I am betting most people will join Twin Adder now that travel between cities does not have any prohibitive cost associated with it (limited anima).

People will of course stay in Ul'dah while just "hanging out", because it is the social capital. All MMO's have a social capital, stop trying to be such a nonconformist crusader against the unfairness of others' conformity and just accept it. These are living people, they are rational, they go to Ul'dah because it is central and they want to be near the most people when just afk'ing in town. Pretty standard for an MMO.