1. They have planned the ENTIRE series from the beginning. There were no sudden plot changes. In fact, the only major change was the switching of Toph's gender. Why would they change their minds now? I'm sure Nick has been riding on them to change other things in the series and they've resisted. Bryke is famous for sticking to their word. It's a one in a million chance they'll change their minds.

2. THE SEASON WOULD BE AN EPIC FAIL! Too, too many TV shows have been ruined my being prolonged. Spongebob (don't hate), Pokemon, Yu-Gi-Oh, and Naruto among others have been utterly demolished by plot extensions. I refuse to let ATLA be ruined too. Okay, so the Ursa question could be answered. Whoop, that's one episode. What will the next 19 be about? You can't just have a random plot. There's got to be some goal of the new season. The previous seasons were because Aang had to learn that element, but why make the next season? What's the point? Answering one question doesn't call for an entire season. That's what the mini-episodes are for.

Please think about what you wish for or it might just come true. Prolonging Avatar would ruin it. Just wait for the movies and the possible new series and/or mini-episodes.

Well, season 4 MIGHT ru??n avatar, but I doubt it. IF Bryke is going to make season 4, I'm sure they are only going to do it if they have a good plot. They haven't got a good one so far, and that's why it probably won't happen. BUT IF it happens, I'm sure Bryke will make it great!