When does Avatar: The Last Airbender return?

Avatar: The Last Airbender is set in a largely Asiatic-inspired world in which some people can telekinetically manipulate one of the four elements. The only individual who can bend all four elements, the "Avatar", is responsible for maintaining harmony among the world's four nations. The series is centered on the journey of twelve-year-old Aang, the current Avatar and last survivor of his nation, the Air Nomads. It also follows the story of Zuko, the exiled prince of the Fire Nation, seeking to restore his lost honor by capturing Aang and his sister Azula.