Battlestar Season 3

Does anyone know when season 3 of Battlestar Galactica will be
out on DVD?

Not sure for certain. Rumors over at the Battlestar Galactica wiki have it tentatively placed at around April 2008 to be around the time the new season starts to air.

http://en.battlestarwiki.org/wiki/Battlestar_Galactica_-Season_Three(Region_1_DVD)