Will there be a new season of Avatar the Last Air Bender?
there will not be new seasons of avatar after book 3.
No, the third season of Avatar: The Last Airbender is the final season. However, it might interest you to know that the makers of Avatar: The Last Airbender are developing a new 10-episode mini series about Avatar: The Legend of Korra. Korra is the avatar after Aang and is also Aang and Katara's daughter.
The third season of Avatar: the Last Airbender has already aired. The third season is titled 'Fire', and is the last season of the series. The final episodes will be aired in America on the 19th of July (2008) on Nickelodean. The show no longer plays on Nickelodean but they do show reruns of it in the aftertoon on weekdays.