James Cameron has given up some details for his upcoming Avatar sequels while chatting to EW, the director revealed they are aiming for a 2014 & 2015 Christmas release:
"I am in the process of writing the next two Avatar films now. We are planning to shoot them together and post them together, and we will probably release them not quite back to back, but about a year apart. Christmas ’14 and ’15 is the current plan."
"Basically, if you survived the first film, you get to be in the second film, at least in some form... Fox has partnered with me to donate a chunk of the profits to environmental causes that are at the heart of the Avatar world... I didn’t want to make more Avatar movies without a grander plan in place."