Edward, a Sega GM, announced today that the Phantasy Star Universe Xbox 360 servers will be shutdown on September 7th. The reason cited for the shutdown was the level of support that could be provided for Phantasy Star Universe Xbox 360 servers while Sega prepares to release new games. Once the servers have been shutdown, only the single player version of the game will be available. Players with an active Guardians license will have their subscription refunded on a pro-rated basis following the shutdown.
You can discuss this news in this on-going forum thread.