My money is on the quiet failure mode. The demographic collapses we see happening around the world continue and spread as more people have the resources to live individually, without family. Through automation we overcome the economic issues caused by population inversion, leisure is the norm, ambitions are confined to personal goals, and the human species coasts comfortably down to nothing.
I think that direction will rapidly lead to people of the "Quiverfull" attitude (not necessarily literally in the Christian group of that name) becoming dominant.
