There are supposed to be 4 Avatar sequels, the first to be released on Dec. 18, 2020 and three more arriving Dec. 17, 2021, Dec. 20, 2024, and Dec. 19, 2025.
The movie industry, at least as it relates to theaters, seems to be dying and although Avatar did extremely well at the box office, its success may have been partially due to it being the first of the new breed of 3D movies back in 2009.
Avatar doesn't seem to have the type of following Star Wars, Star Trek, or LOTR have. There hasn't seemed to be any void without an Avatar 2 or public demand for a sequel.
Cameron wouldn't be putting so much money into 4 sequels unless he felt confident about a return on his investment so maybe this is a straight to Netflix deal where he can't lose financially.