James Cameron's been burying himself in "Avatar" for the past few years, even going so far as to complete the scripts for "Avatar" 2, 3 and 4 last summer -- but apparently the veteran director isn't done with his work on the story, as he wants to ensure the success of the first film wasn't just a fluke.

"I’m in the process of doing another pass through all three scripts right now," Cameron told Entertainment Weekly in an interview. "Just refining. That’s in parallel with the design process. The design process is very mature at this point. We’ve been designing for about a year and a half. All the characters, settings and creatures are all pretty much [set]."

Considering "Avatar's" success as the highest-grossing movie of all time -- amassing $2.7 billion in theatres -- there's a lot riding on "Avatar 2's" performance, especially with two other sequels in the pipeline: "Obviously, expectations are going to be very high on these films, especially on 'Avatar 2,' to make sure it wasn’t just some big fluke the first time...So we’ve got to deliver. I’ve created a nice rod for my own back, so they say."

"Avatar 2" is currently slated for a December 2017 release, followed by "Avatar 3" in December 2018 and "Avatar 4" in December 2019.