Maybe the state could make it so the last person is someone who has no plans to ever leave, such as an elderly retiree. It could work like this.

• The state identifies neighborhoods that will need to be abandoned in a few decades and puts them in a program to turn them into retirement communities. A person who owns a home in such an area can sell it normally if they want to anyone who will buy.

• If an elderly retired person is interested in a property in that area they have the option of instead of buying it themselves from the seller having the state buy the property, and they then pay the state. The state gets title to the property and the retiree gets the right to live in it until they die.

• If the retired person wants to leave before they die (or has to leave because they can no longer live on their own or the time has finally come that the property must be abandoned), they are offered free room and board for life at a state managed assisted living community.

• If they left for a reason other than that the property has to be abandoned the state opens it up to another retired elderly person on the same terms. The new person pays what a similar property in a place not under threat would sell for, and they are now set for housing for the rest of their life as long as they stay there or transfer to state managed assistant living.

• To further make these properties attractive to elderly retirees the residents should not have to pay property taxes and utility rates should be capped. Maybe also toss in a free shuttle service to minimize the need for cars so people don't have to leave just because they are no longer able to drive safely.