I guess it's a James Cameron kind of day.
While discussing and doing press for Avatar 2, producer John Landau admitted that it is now likely the film will miss it's December 2014 release day. He blames it on the fact that they want to take the time to make it "right" which is probably really code for James Cameron is too busy exploring the bottom of the ocean to actually work on Avatar 2.
In all reality, I suspect that it might be at least in part due to the fact that it is hard to blow people's minds and change cinema more than once in 5 years. Or maybe the effects are just so hard, that they are all sitting around looking at each other asking "what the fuck are we thinking trying to do this again?" There is part of me that is really excited for it, and is looking forward to it whenever it's released, and part of me that hopes it's really worth the wait.