I suppose that part of the "big deal" is that he has been talking about it for years. Some of the media are claiming that it is because of Cameron and this film, that we are seeing a re-emergence of 3d films and many cinemas are now upgrading their equiptment as a result. A similar response was around when people heard that George Lucas wanted to re-release the Star Wars films in 3d.
However with all of the financial difficulties at the moment, not as many cinemas will be upgraded as they had hoped.

Daz Studio 4.8 and 4.9beta, Blender 2.78, Sketchup, Poser Pro 2014 Game Dev SR5 on Windows 8 Pro x64. Poser Display Units are inches