I don't think that the neighborhood (fill in the blank) will be coming back either, I was just trying to talk about what it would take for all of acres of housing to enable more livable walkability in the absence of bulldozing thousands of acres of single family homes.
I linked to some study in the last few weeks about how close even bike share stations need to be to be functional -- you could probably base spacing of other needs on that.
I guess it is interesting to imagine what we would do if tomorrow we woke up and gasoline was $25 a gallon and we knew it would only go up from there, but as you say, there are many efficiencies to operating larger "supermarkets" including the ease of logistics and transport to stock the stores -- something that just gets harder if there were many of them scattered about.
Like many really-big-picture problems, all of the participants are not currently working to optimize the same overall goal (whatever that might be), and so the competition and cooperation between different interests will just have to work itself out and adapt as things change.