> My own opinion is that phone's viewport is too small for a great AR experience. It's a nice initial experience and visually impressive, but will quickly become tiring. The long term form of this has to be some form of glasses, because waving around a phone in all directions and holding it in midair while touching the UI is kind of awkward.

I'm 100% certain that's what Apple is preparing for. AR in a phone is a neat toy, a gimmick. The most perfect AR toolkit ever made still won't change the fact that you're holding a phone in your hand, interacting with it through a screen, etc.