I've given this some more thought and decided to revise my description of the possible end of times. This is really more of a cyclical rather than a linear process. This doesn't replace what I wrote before. Instead, that initial post described just one path out of an infinite number of possibilities.
There are two key drivers in any TEotWaWKI story: the breadth and depth of the event and society's cohesiveness.
Each event has a trigger. The malevolence of the event will spread or recede depending upon society's reaction to it and the availability of fuel to keep it burning. Can this be kept under wraps so that the general population is unaware of what's happening? Will the old society be forever destroyed? Humanity's extinction may not be out of the question.
This can play out in any number of ways, as we will see in the stories I review.