The concept of retiring will disappear relatively soon. I don't even think we will be working 8 or 10 hours every day. I think society will make a shift when it comes to work.
People can't help themselves. I don't think we're very close to retiring, it's just not in our social coding.
Today, to live free of work, you need about $500,000. There are groups of people dedicated to achieving this (FIRE / Moustaches). Then you live somewhere cheap, make sound investments, and live off of $25k / yr. In the right places, less than 1/4 of that will go towards rent.
If our primary concern as a society was escaping work, we'd be better at it. Most of our modern economy goes towards making things better, not cheaper (phones, transportation, entertainment, etc.).
We're already at a point where as a society we have the tech to live off of 10 hour work weeks. But we'd have to focus our economy on making a low standard of living cheap, instead of focusing it on raising the standard of living.
When finally science unlocks the secret of immortality, they'll just raise the retirement age correspondingly.