This reminds me a bit of the Bruce Sterling novel Holy Fire, in which soaring life expectancies and prolonged professional careers create a new, more severe generation gap between the "gerontocracy" and the younger generations. Sterling's speculative future didn't include a birthrate decline, though. What happens to our society when younger people become an increasingly marginalized minority?
You would see political gridlock over pension/social security programs cutting back on anything, health care becoming an entitlement program, a casual disregard for running up debts that future generations have to pay, and education costs drastically out-pacing inflation.
