James Cameron has purchased 50 RED EPIC-M cameras for $2.9 million (I wonder if he got a discount because he bought in bulk). For those unfamiliar with the camera, Technology Digital explains that each camera is only 5lbs but can deliver ultra high-resolution, 3D images. Some of the films currently using the EPIC-M are The Amazing Spider-Man, The Hobbit, Prometheus, Jack the Giant Killer, Contagion (although I’m not sure if this film will be in 3D), and Underworld.
Presumably Cameron bought the cameras for Avatar 2 (which is set for release in 2014), but maybe he just wants to give them out as party favors. Or maybe Cameron is just really serious about his home movies and doesn’t want to mess around with a camcorder. But I would say the best guess at this moment is Avatar 2.