A mere three years ago, 3D was heralded as the future of television, bolstered by the overwhelming popularity of a certain James Cameron film starring blue-skinned aliens. Now it's "just another feature" on today's mid- and high-end televisions, and barely anyone watches it.
The main problem is lack of content. There are still only a handful of 3D channels, which show plenty of repeats, and even massive 3D rollouts like the 2012 Summer Olympics met with yawns (it didn't help that the 3D events were delayed until a day after the live ones aired). Films in 3D are still the exception rather than the rule, and glasses-free 3D is still a future technology for televisions. It seems people still prefer both their TV hardware and programming to be flat.
No, 3D TV isn't going away, but it does look like it's going to be relegated to one of those product features everyone has but only a few enthusiasts use.