I think the threat to E-ink use/investment comes from smartphones and QR codes. With those, someone can use a scrap of regular paper to anchor an arbitrarily large amount of information. (Which can also be revised remotely.)
Even the use-case of grocery store price displays are somewhat threatened by "order ahead online."
The downside is you have the swipe down, tap, then scan, not just glance.
Maybe phones could have a dedicated "Turn on and scan" button that doesn't require unlocking for certain things, so it could be frictionless in the way that saying "hey Google" is.
The other issue is that it's cloud dependent, or else only works when you're on the same wifi. There is sadly no special instand connect wifi P2P URLs I know of, unfortunately, much as I'd love to see that happen.
Even the use-case of grocery store price displays are somewhat threatened by "order ahead online."