Seniors contemplating downsizing need to "do the math" and think like insurance companies selling annuities. Does the money you clear from selling your home pay for rent for the rest of your life expectancy?
Another point to remember is that, if a home is really a target for a tear down in the more immediate future, the land price should rise quickly, meaning the owner can get more money by holding out.
It's also well to note that many financial planners advise seniors to be wary of invitations to place "pocket listings" on the theory that these require less time and disruption of the seller. The Washington Blade has a cautionary piece by Tim Savoy here.