If the elderly has any children (presumably they have), those children will inherit the house, rather than sell it at a loss. It would only decrease in price, if the children has a high need for cash, and a low/zero need for housing. This situation is still typically rare (for example, moving away permanently is one such situation). And even in those cases, you will rent out the house, rather than sell for a loss.
Therefore, the most average, and typical scenario is going to have the housing price be stable, rather than drop.
If the elderly has any children (presumably they have), those children will inherit the house, rather than sell it at a loss. It would only decrease in price, if the children has a high need for cash, and a low/zero need for housing. This situation is still typically rare (for example, moving away permanently is one such situation). And even in those cases, you will rent out the house, rather than sell for a loss.
Therefore, the most average, and typical scenario is going to have the housing price be stable, rather than drop.