According to a news item posted at SG1Archive.com, MGM will be releasing Stargate SG-1: Season 5 on January 20th, 2004:
The release date for the Stargate SG-1 Season 5 DVD boxed set has finally been set! MGM will release it on January 20, 2004 to fans in the United States and Canada. (Season 5 has been available in Europe for some time already.) The episodes will all have commentary tracks, just like the Season 4 set. Other features have not been detailed, nor has there been any cover art released.
Thanks to the guys at SG-1 Information Archive for the info, and also thanks to Ron Wolfe for directing us toward this information.
