This whole discussion is mainly off-topic in a thread about 45 Bay. But not entirely, since the mere existence of a large project like the one that includes 45 Bay indicates that this "boom" is still going strong.
I don't think it's a boom, myself. I think that there has been a fundamental change in the urban development pattern of Toronto, which has been done twice before by other North American cities. New York entered this phase over a century ago, and only the Great Depression and WWII temporarily pulled it into a lower level. Chicago also entered this phase in the mid-twentieth century. Toronto entered it about the turn of the century. The obvious common factor would be their sizes. Once the three cities had reached a certain critical level of population and economic activity, a self-reinforcing cycle of development was established. Other factors that determine whether a city enters this higher level of growth would include whether it's the national economic center, and whether their is limited room for outward expansion. I suspect that Toronto was on the edge of entering this phase for a while, but the establishment of the Greenbelt basically made this type of upward expansion in Toronto a permanent condition.
