Rumor StatusBlue Sky
Reportedly there are expansion plots adjacent to Pandora: The World of AVATAR that can be used for a new attraction and a table service restaurant. The only public source on this information indicates the existing of the expansion spots, not that anything is currently in development.
June 11, 2018: On Episode 166 of the Disney Dish Podcast, Jim Hill discusses the idea that the 3rd attraction coming to Pandora: The World of AVATAR would largely play on events/visuals from the 2nd and 3rd Avatar movies.
October 30, 2017: WDWMagic.com user marni1971 is reporting that an expansion to Pandora is fueled by the land not having the operational capacity originally anticipated.
July 14, 2017: Vulture.com is reporting that Pandora: The World of AVATAR has two expansion plots that could be used for an attraction and a table service restaurant in the future.