Yay, this is such great news !! I remember the creators saying that the 3rd book would definitely be the last. Though because of its popularity, and large demand for a continuation, a 4th season is supposedly in the works ^__^. 

http://www.allvoices.com/contributed-news/6168380-avatar-the-last-airbender-season-4-coming-soon

Sweet. They needed to answer a few things anyway, like how the air nomads are going to come back and whatever happened to Zuko's mother.

Awesome!...

I had a feeling they would come out with book 4 "Air".  So many loose threads and issues still yet unresolved.  Although I would have thought they'd wait till they see how the first movie fared.  Either way, I'm so excited.

Cant wait!!! though no more Mako for Iroh! that will suck.

it isn't a rumour or a bad joke, right?

when I click on the link it say 404 not found

but if true..... yesssssssssssssssssssss!!!!!!!!!!!!!!!!!!!!!

Cool. hope they don't screw up but in all honesty, do we really need another season?

everything was resolved when they defeated the Fire Lord.

Pretty much.  There were a few ancillary matters, but for the most part the game ended: what's left to cover?

I was completely content with how it ended.

That said, I'd welcome more Avatar.

I thought book 3 ended the series well, but I'm always up for more Avatar!

Uhm, what? The website doesn't even seem to state a definite season 4. Just kind of states it could be needed. Have they ever broken this kind of story before? If they are some reputable site I don't know about then I'll believe it, but they just seem kind of rinky dink so far.