In the same line as recognizing S.S. retirement may end up a REVERSE Ponzi scheme -- each retiring generation being potentially able to soak even more benefits in absolute terms out of their youngsters then they paid to their oldsters (based on average income more than doubling over a working life span) -- and especially after S.S. retirement settles down to a steady (6-7%) cut of GDP (about 40 years from now)...
...Social Security retirement AGE -- if sanely set; not like in the Moynihan-Malthusian debacle of the eighties -- may actually come DOWN with each succeeding generation. :-O Of course, this will depend on the relative voting power of the oldsters (which will increase for the next 40 years ;-]).
MORE for Malthusians:
Since so much formerly taxable income has shifted out of FICA cap range during the last half of S.S.'s existence, due to the rise in so-called "inequality" (a weak term if you ask me for the wage rape that has been happening) -- assuming we don't get inequality ironed out we can just remove the cap altogether (not just up it a bit -- that would not recapture the income stream that has moved to the top few percent of earners, overwhelmingly to the top one percent -- "rape" might to tough a term since American labor has mostly let it happen to itself via lack of interest or ignorance about bargaining power.)
Impracticality of RAISING retirement age:
Being employable means not just health as in lack of disabling disease, and, not just physical strength (as you point out: the requirement for that has dropped drastically) but also physical energy, attention and, yes, even fully working memory.
Problem is, even if you think people over 60 are just fine in these departments, EMPLOYERS do not. Try to get a job other than WalMart greeter over 60; good luck.I am 64 (this week) and employers are not all wrong. When your muscles go (without heroic efforts, in your very late 50s) a portion of your energy and ambition go that cannot be compensated for by the biggest adrenal glands (which I have); short term memory can become a genuine problem too.