Jake here with yet another update.  Folks, we have been waiting for some major spoilers for a while.  AND HERE IT IS!

July 29th will see the release of the Book 3, Volume 4 DVD.  TVShowsonDVD.com has the following spoilerish info (NOTE: Proceed with CAUTION as the following paragraph contains major spoilers for the finale):

"The kids return to the Fire Nation and prepare for their final confrontation with Firelord Ozai, but they discover that the Firelord has plans of his own: he has ordained himself Phoenix Lord and appointed Princess Azula as the next Firelord. In the spectacular 4-part finale of Avatar Book 3: Fire, Aang fulfills his destiny as Avatar and confronts the Firelord in the greatest battle of the series."

 Wow.  Now that's something pretty epik.  Click the link above to read the entire announcement.  A thumbnail of the cover art is scene to the right, click it for the full-size image.

I assume this would include 316-321, the final six episodes, though there is no indicating on the announcement about that.  Even so, hope this helps to cool your AWS for a little while!