Start off with Apple’s official announcement:

Apple today announced Dan Riccio will transition to a new role focusing on a new project and reporting to CEO Tim Cook, building on more than two decades of innovation, service, and leadership at Apple. John Ternus will now lead Apple’s Hardware Engineering organization as a member of the executive team.

John Gruber’s take (headline linked):

This is not an easing-out-the-door of Riccio: he really is taking over something big and new.

And:

I still don’t know which project Riccio is heading, but my guess is that it’s the headset, not Titan, simply because I’m certain the headset is closer. I think it’s a sign that the headset is ready to get real, and Apple wants someone as capable as Riccio to lead it with nothing else on his plate.

This really clicks for me. Mostly because of something Horace Dediu said in this post about Apple entering the highly competitive car market:

The reason Apple’s market revenue shares are so much greater is because it largely created the markets in which it participates. Rather than hacking out share from incumbents, it created its own and iterated to sustain.

Apple Watch and AirPods are perfect examples here. Folks weren’t wearing smart watches or Bluetooth EarPods (at least not in great numbers) before Apple entered the market and, in doing so, expanded the market considerably.

With Apple Glass (or whatever branding such a product might use), Apple would be entering a failed and tiny market. With a vehicle, Apple would be entering a massive market with many competitors. Like night and day.

I’m with Gruber on this.