It sounds like Ann Arbor is creating what may someday someday become a ring park, like Berlin has. No one is going to stop development without strangling a city - people need places to live. The best that municipalites can do is to try to channel that development in such a way as to make for a livable city. If the majority of Ann Arborites want a green belt, more power to them. But they shouldn't be surprised when suburbs spring up beyond that green belt.