Originally Posted by
Mirage
The vast majority of MMOs are just shut down because they don't have big enough user bases for the owners to earn money on it. There are extremely many more unsuccessful MMOs than successful ones. You don't hear much about these because they've been shut down permanently.
When Squix feel like they can't earn money on FF11 anymore, it will probably just be shut down entirely. They might keep a single server online with no user support or updates just because it is a "main installment final fantasy" and they might feel like such a game shouldn't simply vanish. It's probably not very expensive to keep a single server open for legacy purposes.