Has this ever happened? I have heard this prediction about everything from Toronto to New York to Los Angeles to Hong Kong for years and it has never seemed to come true.
There are people willing to make extreme sacrifices to live in certain places. People will live 5 to a room in cockroach infested 100 year old apartments to stay in certain places.
In Toronto, labour is no more expensive to purchase than the rest of Canada (minimum wage laws aside). Toronto is worth it to enough people to have a bunk in a bunk bed over a room to oneself while working in fast food.
People can also commute. Vancouver is notorious for having teachers commute from Abbotsford. In Toronto, people will commute 2.5 hours each way from Barrie or London.
A lot just may be that the older people get replaced with less resource intensive young people who don't have kids, need less medical care, and are happier in less space.