The effect of removal from the environment will not fade, but the social ramifications for the user will. People are less pissy now when someone stops to check their phone during a conversation, but that's more due to the expectations of those around them rather than our expanded ability to functionally multitask.
Part of the promise of the information age is general cognizance of the fact that we live in an incomprehensibly vast and complex universe, and that we are only able to perceive the most infinitesimal mote of it during our lives. With the judicious application of technology, we can expand our perceptions many times by accumulating information from different parts of physical space. For thousands of years, it was possible more or less to pretend that there was nothing else in the universe outside this room, and no one else alive but your family; thanks to the internet, that is purely impossible today.
It should not be surprising that this frightens some people.
Technophobes frequently protest that assisted communication can't have the value of face-to-face speech, which is frankly complete horseshit. Most of the in-person conversations that most people have most of the time are more banal and purposeless as the front page of Reddit (or 4chan, depending on your peer group). What is important is the relationships that we have with other people, and I've seen nothing in my experience or the literature to imply that relationships are intrinsically less meaningful because they are not communicated in person.
This sentiment is a form of forceful control exerted by those who have no other reason to command attention but proximity. This is also crap; attention is a product of interest and respect. If I am not interested by what you are saying, you will not maintain my full attention for long; and if you demand my full attention for no other reason than that you happen to be the human being closest to me in physical space, neither will you my respect.
I did read your post, I disagree that the tune out will ever end, its just how it's read by others will culturally shift. you're still gonna be withdrawing your mental presence from the space, an externally triggered space-out.
Also of use might be some way for the device to show to other people (not the user) that it isn't distracting the user at the moment. So it doesn't give off a "they aren't paying attention to me" vibe. Perhaps just normal light leakage, or lack thereof, while the display is active/not will be enough for this signal.
My feeling is that this effect might fade away as people become more used to the device. Anyone who wears glasses can tell you that the first time you put them on, the frames are very distracting in your peripheral vision. You become accustomed to them rapidly, however-- within days, the frames are invisible, and you retain this even when you take them off for a while.
A similar phenomenon takes place when driving. Every now and then you realize that you weren't watching the road at all, just driving along automatically with your peripheral vision. And the haptic compass experiments have demonstrated people have the ability to gain an unconscious sense of location from external stimulus.
Obviously something popping up in focus is always going to be distracting, but with a notification icon in the corner of your eye, it's entirely possible that one would grow used to it and stop consciously noticing its appearance-- you'd simply have a somewhat-unconscious "email sense".
And there's no reason that should distract one from what they're doing; when the mail comes to my door, I don't stop whatever I'm doing and go read it. I make a mental note to check the mail when I get a chance, and continue the conversation.
I'm pretty excited about this technology.