There was a very good article a few days ago in The Wrap about the downward trend in 3D box office revenues. (By the way, The Wrap is a favorite publication of mine on the entertainment business. If you don't read it, you should.) While the author (Daniel Frankel) gives fair coverage to the topic, I think the article misses the big picture.
An underlying assumption seems to be that tracking 3D statistics independent of all other factors is meaningful. I'm not sure that's true.
While 3D versions of films currently command a higher ticket price, it is not a separate genre of entertainment. 3D is a production technique, just like Dolby or DTS sound, IMAX, or any number of past innovations like 70mm film or Panavision lenses. 3D is certainly a more dramatic departure than many innovations, but it isn't anything separate and apart from the underlying film.
Films attract audiences because of a combination of good stories, good acting, good editing, and all of the other factors that go into making a captivating entertainment experience. Put a bad film in 3D, and it is still bad (if not worse because the shortcomings are literally jumping off the screen at you).
The assumption that audiences will go see anything just because it's in 3D has never been true. The current numbers are bearing that out. Bad 3D films are performing badly, and good 3D films are performing well. This is not a surprise to anyone.
3D is another wonderful tool in the bag of filmmakers. When it is used well on a good film, it will enhance the quality of the film and probably produce increased revenues. When it is used poorly and/or the underlying film is not well-made, then the use of 3D just means they spent more money to make a bad movie. It won't do anything to increase the audience for the picture.
So the overall decrease in 3D revenues results not from a fading of the attractiveness of the technology, but from the broader use of the technology across a wide spectrum of films -- many of them being pretty bad films. That pulls down the average, but it has nothing to do with 3D.