That's unrealistic. The stronger force would be people's demand for their right to the 'fountain of youth', and they'll back regulation of sustainable birth rate to allow them that longer lifespan, the same way they back carbon credits and other global warming preventive measures "for the greater good", even without solid proof that it's required and is actually effective.
Excessive pollution/fuel waste = govt regulation. Do you expect that the oil shortage and outrage of not being able to buy SUVs can be fixed by just voting in a new govt come next election?
Anyway, this argument's stupid and beside the point. A cure for aging would trump everything else. The vast majority of people would back it. It'll happen. If people can stand for something flimsy like carbon credits, they can stand for reduced birth rates in exchange for longer life. Quality over quantity.