In August 2013, Cameron announced his intention to film three sequels to Avatar simultaneously, to be released in December 2016, 2017, and 2018. However, on January 14, 2015, Cameron announced that the release dates for the three sequels were each delayed a year with the first sequel scheduled to be released in December 2017. In September 2017, the sequels to Avatar started production with the plan for the first to be released in December 2020, the next in 2021 and a further two in 2024 and 2025 respectively. Deadline Hollywood estimated that the budget for these would be over $1 billion in total.
Avatar 2 and Avatar 3 started preliminary shooting simultaneously in Manhattan Beach, California on August 15, 2017, followed by principal photography in New Zealand on September 25, 2017. The other sequels are expected to start shooting as soon as Avatar 2 and 3's filming wraps.
Although the last two sequels have been greenlit, Cameron stated in a November 26, 2017 interview: "Let's face it, if Avatar 2 and 3 don't make enough money, there's not going to be a 4 and 5".
At the rate that he works I doubt there will be time for him to direct any more feature films after that.