James Cameron is one of those film directors that has a lot of huge landmark films to his credit like The Terminator, Aliens, The Abyss, Terminator 2, True Lies, Titanic, and Avatar. Considering that Avatar made so much money as the biggest film of all time, one would think that he would get out a sequel as soon as possible. However, Cameron has a reputation for taking his time, and this is what is known about the Release Dates of Avatar 2, Avatar 3, and Avatar 4.
The IMDB page summarizes the second film as "a sequel to the 2009 global phenomenon," which is as vague as possible. A recent report from Movie News Guide states that the makers have come to the conclusion to have a plot themed on war with prisons. This probably means that more humans are coming to Pandora, and this is going to start a planetary war between Earth and the Na'vi.
It is reported and confirmed on the IMDB page that Stephen Lang will be reprising his role as Miles Quaritch and that there will be some "unexpected changes to this character." Also returning are Neytiri (Zoe Saldana) and Jake Sully (Sam Worthington). Even Sigourney Weaver's character Grace plans to reappear, in spite of having died in the first film. Not making an appearance is Michelle Rodriguez as tough pilot Trudy Chacon.
Unlike most films, where a second and third movie is planned, Cameron wants to do three movies. A suggestion would be to have Avatar 2 begin with an army from Earth invade Pandora, and end with the Na'vi losing this war, possibly in prisons. Then, in Avatar 3, Jake and Neytiri start a rebellion on Pandora and eventually defeat the Earth Army on the Na'vi's homeworld. Avatar 4 would then conclude with Jake and the Na'vi using some starships and invading Earth. At that point, audiences would have to ask if they want Jake to win the war and destroy all humans.
That is just a synopsis of the main plot, and there will be a lot of secondary plots as Jake and Neytiri will develop their relationship. There has been a lot of talks that the war between the Na'vi and the humans will separate them, for good reasons. After all, Jake is originally a human. As for Stephen Lang's character, he could be the grand villain of the next three movies, but it is likely that his character could go through a transformation. That is, he might end up joining the Na'vi in the fight for their land.
Of course, that is all speculation and just fan theories at this point, but it is revealed that Avatar 2 will focus on new creatures, underwater sceneries, and more of the rich ecosystem of Pandora that made it so beautiful in the first place, according to the International Business Times.
Fans should look forward to a release date of Avatar 2 on December 25, 2017. As for Avatar 3 and Avatar 4, they are expected to be released in 2018 and 2019.