Season 6's release was announced on September and released on December, so there's still time for CBS Paramount to announce the release of Season 7. Since they completed Laverne & Shirley and Mork & Mindy I don't see why they wouldn't release all HD seasons on DVD.
"All our dreams can come true, if we have the courage to pursue them". ~Walt Disney
"Sometimes I just don't understand human behavior"- C-3PO