I’m pretty sure that ‘ideal form’ here is a pair of regular-ish glasses. That ain’t happening in four generations unless you’re going to be real creative about what a generation is. It certainly isn’t four years away, like the analogies to iPhones and Apple Watches implies. That’s going to require an absolutely wild amount of innovation to achieve. And, even if that happens, such new technology is going to take many further generations to become remotely affordable enough to be priced for anything like mainstream adoption. Pile all that on top of the lingering curiosities about what problems this interface model actually solves, and the cultural shifts that will be required to get people comfortable to accept pervasive face cameras in social settings, and you’ve got a product line that has niche appeal written all over it for at least another decade or two.