I know this may seem a bit far-fetched and it could very well be but YouTube partner and host of the weekly YouTube show, "Movie Buzz" Peter Rallis has come out and stated that Avatar 3 is set to begin filming this November. Apparently, Avatar 2 has wrapped production earlier this year.
I don't know how true this rumor is but for now I'm leaning toward true. If Jim Cameron wants to release these films Christmas of 2014 and 2015, post-production would need to begin about now. After all, Avatar was in production since March 2008, well over a year before its release in December 2009.
Check the first minute of the video after the jump for the special announcement:
Let's hope that this rumor isn't proven false.