Tales Channel was updated with a release date set for "Tales of Symphonia: Knight of Ratatosk/Dawn of a New World" for Japan. It is set for June 26th, 2008. I don't know if there was an existing release date for this, since I had no knowledge of its release date in Japan before this update.
Tales of Symphonia: Knight of Ratatosk (Official Website)
Edit: To those who are wondering about the sudden change of release date, the game got delayed. -a745