And how soon?
Of course this is all conjecture, but I would think that everyone has an opinion on this.
There are many different scenarios that could bring on The End Of Days -- anywhere from man-made disasters (Yellowstone blowing or a Comet strike), nuclear war brought on by any of a number of dangerous confrontations, class warfare, race warfare, total world-wide economic collapse ......... just to name a few.
In most of these scenarios, I see the big cities emptying out. As the grid goes down, it will all fall like a house of cards tumbling. And we will become a desperate society so quick it will make your head swim.
If you've paid any attention at all to the news in the last few years, it is like a boiler getting ready to explode, in all directions. Therefore, whatever is coming ... I think it will be within the next few years -- five at the most. While race and class tensions are at an all time high, I think it will actually be a nuclear confrontation that sets it all off. North Korea, Iran, ISIS taking over Pakistan (with all their nukes), Russia feeling their oats, China doing ....... whatever the hell those slant-eyed bastards are up to (and the west will never figure them out). Our biggest problem is that we have no standing anymore in the world. All these renegade nations know that we can't even talk a good story anymore, let alone control things. So, the world is a VERY dangerous place now, more so than ever before. Too many pirate countries have gotten access to the bomb. On the other hand, we don't have the foresight or guts to take down a renegade nation BEFORE it all gets out of hand.
Maybe it is just the musings of an old fart late on a Sunday night --- but I see it coming and relatively soon.