IMO, the traditional meaning of retirement is going to change, first of all in the fact that many people will either choose to/or have to keep working in some capacity, and second, for those who do have the money to not have to work, it will be more active and a whole lot less of the old stereotype of someone getting bored out of their tree around the house, or playing shuffleboard somewhere. If the "retirees" are in reasonably good health, they will most likely be travelling, continuing their by-now-solidly-established physical fitness routines as appropriate for their bodies, or starting up a small business/consultancy of some sort if they haven't already done so. But for those who DON'T have boatloads of money(not even close), we will have to exact some sort of income until the day we drop. That doesn't have to be all bad, however, especially if one can find some mode of being self-employed. Computers are great for this!
As for myself, I have a saying, "Artists never retire - they just might change media!" meaning that age should never have anything to do with doing artistic activity. Many artists work until their eyesight fails them altogether, well into their late 80's, 90's, etc.
My husband started collecting SS two years ago, but he picks up jobs here and there. We've basically lived on one part-time job for many years. We can do this as we live simply and there's an amazing amount of stuff that we DON'T spend money on. We never went for the whole nine yards as far as having the expensive house(we've never owned property of any sort), cars, clothing, etc., nor cared to, so simple living has been in our daily life for a very long time now, whereas there are many people who are only now starting to get the idea that it might be appropriate now to downshift, to allow for changing lifestyles and reducing overhead. Our health continues to be very good, which we hope will continue to be the case for a very long time. One big medical expense can wipe out the best-laid of plans. We have never had health insurance our whole lives - we instead instigated the DIY model which consists of very healthy living.