Interesting theory, but I suspect the Toronto greenbelt doesn't stretch all the way to Guelph.  The problem is more likely that more people want and expect to own a house, and also that there are also some well-to-do people from outside the country who are getting into this market,  because Canada is a safe place to live.   The idea of doing away with public green spaces and making them into suburbs for the well-to-do may tickle  the fancy of some, but I doubt it would be best for the majority, or for the quality of life in general.