Normally you see advanced technology being designed for niche markets and once they get a grip on the market (and usually becomes cheaper) it moves into mass market.
With Google Glass it seems it may go the other way around. They have been designed having in mind the mass market (their biz model was to get ads on the move...) but now we see that they are being used into niche markets.
According to some commentators Google Glass failed. It is now over two years that they have been announced and they haven't been able to make inroads in the mass market. The expectation was raised high and probably this is making the analyses even more grim looking at the present situation.
There are some specific technical hurdles and some technology-social related hurdles.
The visor and the energy consumption are purely technology hurdles: there is a need for better visor in terms of image quality and seamless inclusion in the frame AND there is a need for a power consumption that can be sustained by a small battery for a whole day. These hurdles are likely to be solved in the next two years as new technologies are becoming available.
As an example, Lumiode is perfecting a technology based on micro LEDs. Normally the LEDs provide a uniform light that is filtered by coloured filters overlaid on each LED. The problem is that the filters dramatically reduce the brightness of the resulting image. The approach taken by Lumiode is to have a transistor overlaid on each LED to tune the light wavelength (color) emitted by the LED. This leads to an image that is 10 times brighter.
The power budget will probably take more time to find a fully satisfactory solution and will require progress in both hardware and software. However, intermediate solutions allowing some 8 hours operation might be sufficient to stimulate adoption.
The technology-social issues might be more difficult to tackle. The uneasiness of some people in wearing the Glass and conversely the uneasiness of people when confronted with people wearing Glass is not easy to solve "technically".
On the purely technical side there are some disruptive solutions being considered, like having a contact lens that can magnify the image created by the screen, thus making the screen seamless integrated in the frame and invisible. Clearly, the drawback is that one has to wear a contact lens and get used to it. At the same time, the invisibility of the "Glass" to third parties may look a bit like cheating people who will be exposed to the Glass without realising they are, potentially, observed by an electronic contrivance.
As I said, many observers are considering Google Glass dead as a mass market product. May be they have served the use of really understanding what would be needed for a wearable device to be a success and a new version, not necessarily from Google, may be in the works somewhere...