What makes you think that this is a "fantasy product?" You know that it's already been done reasonably well six years ago by a small startup called North? They made a nice pair of smart glasses that really met the need that people find useful - an augmented HUD where you can visually (and privately) see notifications, alerts, and general information.
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They biggest problem they had (in 2017 mind you) was weight and battery life. Both of these things should be able to be significantly improved in the 6 years since Google acquired North and brought the tech back in for "refinement." The error Google made was buying the tech and not keeping the engineers. The Google Glass team took over and never released any implementation since then. This is exactly the type of thing where Apple can excel. There are multiple iterations of "Smart Glasses" out there, but none of them have gotten the formula quite right. This is where Apple can execute their proven game plan. They don't try to be the first out of the gate, they want to be the first one out of the gate to get it right. There were "smart phones" before the iPhone - Blackberry, Palm Treo, WinPC phones... but iPhone was the first to get the formula right. (And even it needed some refinements before it was at a "can't live-without" level of functionality.) There were previous MP3 players before the iPod, previous laptops before Mac notebooks changed the quality expectations, other tablets before iPad took over the game. But when Apple gets things right... they tend to change the market.
The key is that whatever the Apple product ends up being... it needs to be Glasses focused and discreet technology. VR tech is a non-starter (and Timmy C. has even been very pointed that this is an AR product not VR). But if they come out looking like a silly pair of ski goggles, the use-case will be very limited. Something like watching movies privately on an airplane limited. And until the use-case grows... sales will be limited.