Zoe Saldana recently gave an interview about her character Gamora in Avengers: Infinity War with the LA Times, but she also gave an update on Avatar 2 in the same interview. Don’t read the full interview unless you don’t mind spoilers for Infinity War. Saldana mentions that they are currently finishing up the motion capture work for Avatar 2 and Avatar 3 at the moment with the next part being pre-production on the live-action shots. They will then shoot the film in New Zealand. Here’s her full answer:
Avatar 2 is currently slated for a December 18, 2020, release.