The single most important and most revealing aspect of this announcement is Apple's framing of the promotional images showing the face display on the front of the headset.

I think the large R&D investments tech companies are making into VR/AR headsets are ultimately centered on the idea that years in the future, an affordable, comfortable, and socially acceptable headset for all-day wear in daily life could hypothetically replace smartphones, tablets, laptops, and screens.

If a future daily wear headset as a phone/computer replacement reached a critical mass of adoption, then control of the platform will provide the owner with a huge profit source in selling virtual goods that can be "worn" or "placed" in the real world and are seen equally by any other person wearing a headset. I won't speculate on exactly what would be popular, but it is conceivable that this could include things like: buying virtual wall posters of licensed characters, virtual landscaping objects placed outside a house, filters that virtually "repaint" the exterior or interior of a house, or personal adornments like virtual clothing or appearance modifiers. That is to say, a digital layer of adjustment on top of the real world where everyone wearing a headset is automatically shown the virtual objects or adjustments that anyone else has made (within the scope of the latter's own appearance and owned spaces - random members of the public could not place publicly visible digital objects in the middle of a NYC street). Note that this virtual economy is a profit motive for a company to build AR, but not the selling point for a headset adopter.

Apple is not trying to sell this headset to consumers for $3500. They're showing off future hardware that they believe represents the bare minimum for what average people might be willing to wear regularly, with the expectation that they will be able to produce essentially this same unit and sell it for perhaps a third of the current price in several years. The way it's presented is also an early form of reputation management for the product space trying to influence public perception of how someone wearing a headset is viewed by others around them.

Standard see-through AR headset designs face fundamental implementation limits with the display technology that generally result in accepting one of two unacceptable limitations: a display that projects an image over the real world but cannot render black or otherwise draw anything darker than the scene behind it, or a liquid crystal light modulator with a polarizer that permanently makes the glass tinted dark like sunglasses even indoors. Apple is instead making a VR headset that is completely enclosed, displaying the world through pass-through cameras and drawing the wearer's eyes on a front display for everyone else to see.

The front lenticular OLED shows how Apple is approaching the social aspect of trying to market the acceptability of wearing a headset in the company of other people. In the long term, establishing a virtual economy for digital world overlays is fundamentally dependent on the social acceptance of wearing an AR device regularly. This announcement seems to be trying to thread that needle in advance of when this technology could eventually be priced and sold as a consumer product. I.e. establish an image of an Apple headset positioned without the kind of negative associations Google Glass quickly garnered.

I have no idea whether AR will succeed in replacing smartphones years from now or fade into obscurity, but what I find interesting about this announcement is that it makes a timeline where AR does take off at least appear conceivable. They've only taken a first and early step into trying to make it happen, but they haven't made a fatal mistake yet.