I see only three paths of progress: a) space colonization (however that may work, I don't think there's a way) b) embracing stagnation (in all countable units

I see only three paths of progress: a) space colonization (however that may work, I don't think there's a way) b) embracing stagnation (in all countable units, except perhaps transistors) c) buildup to violent collapse (which may or may not be followed by something capable of written history) b in particular goes far beyond just "a sufficiently large number of people don't procreate", because if it's not somewhat evenly distributed, all future generations will be descendants of high-reproduction ancestors and you're back at square one.