They wouldn't do this if the conversation is important to them. Not as much as one would glance on a smartwatch when they get a chirp, which, I believe is perfectly socially acceptable in most business/casual situations.
And if they do it's nothing new - it's a literal equivalent of talking to a person deep into their phone. Exact same audiovisual media consumption - just a different form factor and display technology. Or, in a pre-phone era, a newspaper.
I don't think this technology introduces anything new to this issue.