The trio of movies are being made back-to-back-to-back by filmmaker James Cameron, said the Hollywood Reporter.
Earlier, Stephen Lang, who played mad Marine Colonel Quaritch in the 2009 film, was signed on for all three new movies.
Jake Sully and Neytiri, the characters played by Worthington and Saldana, respectively will have kids in the forthcoming series.
"Jake Sully is a rare combination of passion, strength, street smarts and soul, which requires a lot from an actor. Sam brought to the role a combination of sensitivity, vulnerability and strength.
The first sequel will hit theaters in December 2016, with the second to follow in December 2017 and the third a year later.