I do not see this product in this form ever being huge. It is great, I am sure. But I personally look at this and feel no desire. This is the first major new Apple product that has hit me this way in...decades. I am old, I hope that it is highly successful.
This is the first iteration. Mostly targeted at early adopters, prospective developers, and anyone who's got plenty of money and just wants to show off the latest tech gadget.
This device won't sell in huge numbers, but it will prove whether there is a market and give an opportunity for developers to come up with some AR "killer apps" that will induce demand for future versions of the headset. Future versions which will, no doubt, be smaller, lighter, and cheaper!