Populations are aging. As Doug Saunders writes: The world’s losing its workers. How will we compete? – The Globe and Mail. Doug’s column is a good one, and the notion of Peak People is a smart one. Like all his columns, it’s well worth a read.
To see how this might affect the world, it’s worthwhile to look back to the 14th century and how it was changed by the Black Death (Wikipedia). Vast amounts of the world population was lost in this century, with estimates up to half the population perishing from the disease. This had a profound affect on the world, as touched on in this column: How the Black Death Changed the World | LiveScience. I expect the same thing is going to happen in the 21st century (something already visible).
I also expect other changes, like a decline in global warming, more democracy and economic equality, an even greater focus on geriatrics, and a greater appreciation and support for children and families. A population that is declining and aging will drive all this.