I think that if a serious extension of life becomes a reality, it will be very expensive. Otherwise, it is necessary to limit the birth rate, or even forbid people to have children.
Not necessarily. If humans can become truly immortal, we could explore the entire galaxy and believe me, we have plenty of planets there to live and spread, we wouldn't need to stop having children at all.
Until mankind invents technologies to explore the entire galaxy,hundreads or thousands of years will past.And if people find out how to become immortal it will be a diaster because of overpopulation,and probably there would be many social conflicts between those who can afford it and those who can't