Mike & Bryan are making another avatar series, they didn??t confirm it but they hinted it a lot of times, like in CCSD 2007 when the little kid asked is this the last Avatar season they said "For this Story, yes.". and in many interviews when they ask what??s next for avatar they said it??s on the early stages but will be planned out.
So guys, Don??t cry that there??s no book 4 and make petitions about it. There??s gonna be a whole new Avatar series (Avatar: _____) with new main characters and seasons. Personally I think there??s going to be a trilogy (Avatar: The Last Airbender, Avatar: The second series, Avatar: the third and final series).
oh, and if it doesn??t happen........
NICK MUST DIEEEEE!!!!