The legend of Korra was awesome. The last airbender was everything I ever wanted.... except now I want more. The Avatar world is so well thought out, beautifully crafted and meticulously maintained, and getting a third great series when you've already pushed a sequel to as many heights as The Legend of Korra achieved...sounds insane. However, ending with so many unexplored corners of the Avatar world....I don't want that to be the final farewell...so I got to thinking.
What about a series that deals with the forever death of the avatar?
Avatar the last airbender described it briefly, the legend of Korra showed us that it could be done, and the final installment would be the world rebuilding itself after this happens...basically the harshest idea since ever right? ;s sorry.
The world was never meant to have the avatar as long as it did, and the main supporting characters in both series share the same commitment to good as the avatar did, sometimes with more conviction, or better skills. It would be heartbreaking, but honest, and would probably be the easiest way to completely end the Avatar without ruining the quality or originality.
anything else wouldn't end the series, it would just lead us on for more.
Extra ideas would be that this avatar's death would happen while they are in their prime (20-35) , that they would not go out lamely, that they had established a group of friends and companions to aid them, that the death would be at the end of the first book, so as not to ruin everybody, and that the friends and enemies would not just get on with their lives. ...that dealing with the death takes an entire book all to itself. ...and no "surprise everyone is here to help" moments either. The first Avatar was not the most powerful bender of his time, and both Aang and Korra were weaker than a single human at multiple times during their series. whether it is Azula or Zaheer, an army or a monster, the only reason why they could make it as far as they did was because of their friends. The bonds we choose to tend and make are strongholds of defense that never break.