I think the cheaper version will still be around $ 2000 because of the display. For me that would be cheap enough to buy one if the software is fine. Maybe they could indeed switch to an iPhone processor and require a connection to a Mac for more demanding apps. But you have a good point about AR, they will still need that 2 chip design so AR features like the hand gesture controls will work well.

If they would want to get rid of OpticID, they would have to require other Apple devices for authentication or introduce TouchID on the device. So they probably also want to keep that.