As far as AR (Augmented Reality, or the use of computer generated content to enhance our view of the real world) is concerned in this context. I think we are a LONG way from seeing AR Glasses replacing smartphones in the literal sense for a couple of major reasons. 1) Until we have a battery tech revolution, there's just NO way glasses will provide the housing and support needed to power the radios for high-speed, wireless communication (forget everything else even). 2) Fashion is a fact of life and I'm willing to be quoted as saying "the majority of people not already having a need to wear glasses are not going to adopt the fashion or hassle unless the glasses are as or more light and unobtrusive as a decent pair are not (without all the tech)." 3) There is SOO much more flexibility in the combination of a smartphone/tablet/belt-computer/etc.. AND AR glasses because you could work without the glasses, minimize battery weight in the glasses, reduce cost by minimizing the need to micro-scale EVERY aspect of the technology, etc..
More than 10 years ago I saw the future of computing and tablets were the first call I made that came to be. A form of AR will be my 2nd and I've kept quite on the public front while I sought out investors for patents and/or a product, but I think the technology as a whole has gone far enough for me to begin to share my vision publicly and it's really not far from what's already come to be in many places, but I'm yet to see the complete picture that I envision, come to be anywhere else and in the end, I DO see AR glasses becoming a standard at the desktop. I think I'll just have to write a paper here soon to go in depth, but that said, I just don't see it becoming the defacto-standard for mobile displays. I think we're more likely to see some sort of viable live-holography come to life and be implemented before that happens (and that is also an idea that a ways off).