A substantial realignment in the economy is what's coming. The charge will be when the rate of vacated homes starts to uptick as their aren't enough capable people to live in them: right now the major metros have a lot of pent up demand, but those retirement figures imply a different reality as time goes on: eventually those people start going into care facilities, but their won't be nearly enough people around to supply the demand for the properties they're finally moving out from.
The real markets are absolutely not ready for that reality.
> right now the major metros have a lot of pent up demand
The major metros have the least to worry about from this. Those cities have high housing costs because of demand, or to put it another way, those cities have high demand despite high housing costs, and the economic factors that cause people to be attracted to cities aren't going to go away; density is devastatingly efficient and it's cheaper and more convenient for people to be close to things. But what this means is that as the population falls, that latent demand causes the less dense, lower-priced areas to depopulate. See Japan's crisis of rural depopulation, and how Tokyo isn't the one feeling the pinch.
Case in point - Japan, with so many abandoned homes
In the countryside, I doubt that this is the case in Tokyo.