Both the DVD and Blu-ray will include all 23 episodes, plus bonus material such as featurettes, commentaries, deleted scenes and a gag reel. The Blu-ray will include exclusive additional featurette, and UltraViolet digital downloads of the episodes (available only in the USA). OH BOO!
No words as yet as to which episodes will have commentaries and who will be featured in the commentaries. It's pretty safe to speculate that Sera Gamble, Ben Edlund and Robert Singer will be doing the commentaries. The surprise, if any, would come from the cast themselves doing the commentaries -- i.e. Jim Beaver doing one for Death's Door, or Misha Collins doing one for The Born-Again Identity, or Jensen doing one for Time After Time, or Jared doing one for Plucky. Who knows! That's just me talking! And you know what I've always wanted? The behind the scene interviews and/or footage from Comic Con. A fan can only dream!
Watch this space for more details..
Here is the official season seven description for the DVD:
"The seventh season of Supernatural put the Winchester brothers in a terribly lonely place. After losing their good friend and ally Castiel at the beginning of the season, the writers systematically stripped away many things that they loved, including Bobby's house, their beloved Impala, and then Bobby himself. Although both Castiel and Bobby returned towards the end of the season, it's clear that Team Free Will isn't what it once was. Not to mention the fact that they spent the season dealing with flesh-eating monsters called Leviathans."
Useful links: Amazon, TV Shows on DVD, TVOvermind
UPDATE: The back cover art work is on the Amazon website, see below. I actually haven't found any release on the actual special feature items, but Supernatural Fans Online posted a few details on their website.
Stay tuned for more update as WB releases more official details.