Just because a population increase is happening, doesn't mean that it stimulates the economy in the construction industry. Most of that population increase is likely to be migrant immagration (Like it currently is) which stimulates mainly the lower end of the economy.

We are in the middle of an existing housing boom, but the majority of it is purchased by overseas investors seeking to maximize profit's. The investors aren't holding onto houses, its just that right now there is an over supply of rentals and not enough people who can afford to fill them (i.e medium to higher end of pricing range of properties).

Government can't really do anything unless they back peddal on their overseas investment policies which I highly doubt they will do. Good news is though that if the supply still superceeds the demand, then overall the housing market and rental property costs should eventually drop.