Most people are too appearance and fashion-conscious to want to wear tech on their face, and I don't see many people wanting to carry TWO expensive tech gadgets (and worry about charging/losing/forgetting them), so, seeing as photos and video is core to what people want from their mobile device, it seems that the smartphone will continue to be the form-factor of the future, and I expect these other next-gen form factors to fail.
I think Apple's brand loyalty buys them some lead time in being a fast-follower, but the danger to them would be if things change so fast and profoundly that they get left behind a la Nokia. What if Google or someone else comes out with an AI-centric "personal assistant" device so compelling that it massively ups the bar as to what customers expect from a mobile device (in same way that iPhone did at launch)? I wouldn't expect it to kill Apple overnight, but it seems that they are in effect gambling that "we can always pay for AI if we have to", and "someone will always license it to run on-device if we need to".
Only the paranoid survive !