The new Avatar series is out Avatar: The Legend of Korra
So the avatar series have started again with a new avatar, and hopefully with a good story to it.
Additional info:
It aired on Nickelodeon on April 14, 2012. The series is currently under production and is expected to run for two seasons and a total of twenty-six episodes, with options for more.
The new series is taking place seventy years after the end of the Avatar: The Last Airbender story, continuing with Korra, the Avatar after Aang
The show have now been running for three seasons:
Book one: Air
Book Two: Spirits
Book Three: Change