Amazon are now showing the back cover, as well as the front, to the Season 5 DVD, due for release on May 21st (and a day earlier in the UK). The back cover, of course, contains all the extras information, and here it is:
And the Blue Ray version:
No mention of Alexander Skarsgard in the audio commentaries, which is hopefully just an oversight, and fingers crossed, there will be one for us to enjoy somewhere in there.