Nice sketch! However, I think you deeply undercut your argument here. The point of Alexa will gradually be that no one should ever need a “just in case” PC. Sure, there will still be uses for screens and computers, but they’ll become more specialized and professionalized – used by people who know why they need them and how to use them, not by people with an abstract sense that they should have a PC “around” “just in case”…
But, maybe I’m missing your argument. What “just in case” applications aren’t covered by Alexa and a screen? There are Alexa-enabled big screen TVs coming. What then?