Preview shown on April 19th.
Some of the important questions asked during the Q&A:
Q:Will there be a 4th season of avatar? There are 4 elements, and since we did water, earth and fire, book of air is still left.
A: There will be no 4th season.
Yes there is the air element, but Aang already had that ability master. (He IS the last air bender after all.)
Q: WE WILL HAVE NO MOAR AVATAR ..NOoo!! *sob*
A: According to the creators: They have two more weeks on the Avatar the last air bender, and thats it. They are done.WITH that story.
But From what Bryan Konietzko and Mike DiMartino said during the Q&A; the world of Avatar is still rich with concepts and ideas they could explore further.(perhaps with a whole new series??)