This is a weak discussion, but an important question. Aside from the obvious questions of who pays for people's pensions, how much should people be saving for retirement, what is the impact of two income households, and who raises the kids in the meantime, the central problem is how do people sustain employment and careers over a period of 40 or 50 years?
Anecdotally, people are entering meaningful employment later in life, and finding a host of obstacles as they age. So meaningful employment has been reduced to somewhere in the range of age 30 to somewhere in the range of age 50. Outside those 20 years you're flipping burgers, going to grad school, or taking early employment, consulting, and greeting at Walmart.
My guess is that as the baby boomers continue to reach so-called retirement age they will transition not from work and careers but from the unemployment and underemployment to social security. We might want people to work until age 71, but most folks won't be that lucky.