3D will take off when they have 4K displays and passive glasses
The active glasses are just a no go for people. They are expensive, needed to be recharged or have the batteries changed, and just don't work well at all for people with prescription specs. The only reason we are getting them is that you can add 3D to any existing TV using active glasses without increasing the cost of the display.
If we move to passive glasses we run into a few problems. Because of the way passive technology works, you can't just add 3D to a display for free as easily. You can do what LG and Vizio are doing and show two 1080i frames at once. This causes you to loose about half the detail of the picture compared to a regular blu-ray though. The second option is to put an active shutter in the screen itself. The problem with this is that you increase the cost of the display substantially. It's much easier to sell the 3D TV when it's the same price as last years 2D TV.
The third option is to combine the showing of two frames at once with a 4K display. Instead of two 1080i frames you get two 2160i frames. This way you don't loose any detail. This comes with an added bonus as well. Even though your TV now costs more than the 2D model, you can sell it as being 4K. Even though the average screen size and viewing distance don't require 4K, we've learned from the megapixel and megahertz wars in the past that you can use a bigger number to sell more things.
