The other issue is capital gains. Some states have a cap on equity (primary residence) which isn't subjected to capital gains and the older boomers who live in expensive states (ex, California) are finding out that they will have to pay cap gains on some portion of their sale proceeds. The tax acts as a deterrent from selling.
If you have to use this to deter selling, the community is already not worth coming into for the new families. A house is only worth whatever the next guy is willing to pay for it. Whether it is due to aging or cashing out someone new has to be willing to pay for it to worth that much. In the end you need jobs and safety to be worth something.
If everyone wants to buy a Chrysler Sebring and then there is a glut of them when the owners pass away, they are only worth what they would sell for for everyone currently still own them.
If their homes are in the right location and the right quality they would be able to sell them. If they are just "customized" in a wrong place (no job) then it is not worth much.