It isn't necessary to imagine the world ending in fire or...

It isn't necessary to imagine the world ending in fire or ice. There are two other possibilities: one is paperwork, and the other is nostalgia. Eventually within the next quarter of a century, the nostalgia cycles will be so close together that people will not be able to take a step without being nostalgic for the one they just took. At that point, everything stops. Death by Nostalgia.