I feel like for it to be mainstream it needs to be borderline invisible (or just looking like normal glasses). Bonus if it can just be contacts (yes I know science fiction here).
Part of the reason I think Apple is in a place to possibly actually make it a thing though, is their track record of taking an existing category and fixing usability issues. See Tablets, Smart Watches... and of course Smart Phones.
They have also been building their AR platform for years and been getting developers to use it. If they are smart with how they have done that, the work for those apps should "easily" translate to this device.
That being said cost is going to be a major issue here, as well as size like I already mentioned. But unlike a certain company... Apple is not known for abandoning projects and I would hope that they are smart enough to realize that this is not a device that will make a profit in the short term