Nickelodeon announced today that not only are they planning a new animated TLA movie, but they started a whole new division named "Avatar Studios" to make future Avatar related content: https://ew.com/tv/nickelodeon-expand...animated-film/
Not only that, but series creators Michael DiMartino and Bryan Konietzko will be leading this new studio. After the disappointing news of them dropping out of the planned live action Netflix series, things are looking up for the Avatar universe.