"Floodgates" of retirement are an illusion. With advancing age, the natural attrition smooths out the process. In the last 5-10 years of any pilot groups working life, a greater proportion will become medically unfit. Some will reduce their working footprint by such vehicles as part time working. A few will avail themselves of other opportunities. By the time that group reaches age 65 any projection of a " flood" or "bulge" is usually little more than a trickle.
Despite the perceived lure of retirement, for many people it focuses the mind on the limited timescale to achieve one final fiscal sprint. There is also the realisation that The job forces you to keep active, and for many that becomes an important motivator. Pilots at this end of their careers are also likely to be enjoying the best of the respective terms & conditions on offer, and would likely want to enjoy that for as long as possible.
When retirement was typically 55 it was more likely that a greater proportion of any given group would achieve that milestone. A retirement bulge (although still rare) was more conceivable. A decade of more gradual attrition simply provides for a much more gradual slope. Add to that improvements in maintaining medical certification standards, and the process becomes even smoother still.
In summary, retirements are a false hope. The real opportunities are going to come from economic growth.