I'd argue that part of the reason why the property market is booming is the rate of household formation, which is outstripping population growth (ie average household size falling and more homes needed for a given population due to divorce rate, smaller families, more living along, ageing of pop, etc). Note that this is not a necessary condition, however, as the same trends occurred in the early 90s, where prices were stagnant.
Neil Jenman pointed out the household size trend in a recent talk:
Early 1900s: Avg new house 2br, Average household 4 people
2003: Average new house 4br, Average household 2.? people
Therefore population can be stable, but demand for housing can still grow. This is a long-trend trend that's been going on for the better part of a century. For it to reverse, there would need to be some social and economic changes, eg swing back to larger families, more people sharing houses, communal living, etc.
Given that flats/villas are a higher proportion of houses in capital cities than in country centres, I can see well-located quality villas being good long-term rental propositions in regional towns, even those showing negligible population growth. By quality, I mean air-conditioned, brick & tile and with garage/storage space.
Peter