I do not see Montreal becoming more important as a North American city probably because it is an island city restricted to the island and because of the language issue that hurts the influx of investment into the province and into Montreal. Quebec is also the most taxed province in Canada and that too would deter people to come and open up a head office here.
I think Montreal reached its peak around expo time and that was when a metro was constructed, the Olympics happened in the city and there were other developments that occurred over the period like the extension of the metro, and the redevelopment of the downtown to include many high-rise bank buildings. The period I am thinking of occurred between 1967 and 87 plus or minus a year or two and that comprised the introduction of an expressway to Montreal, and the building of an Olympic village to the area near the stadium. I thought over language like having to better my French to remain in the province and that may Anglophones wanted to leave because of that requirement and the enforced need to work in two major languages. The language and tax issues did not occur to me as the main reasons for the stagnation of the provincial economy or its stagnation. Critics will say that the stagnation occurred alongside the recession that had occurred all over North America, in the early nineties and was not a product of the double taxation scheme for provincial residents or the fact that the city had two competitive cultures.
Now that Toronto has increasing become more competitive and that Ottawa has expanded to four times the population since the sixties and is home to some of the latest museums, Montreal will likely coast ahead as one of the most important Canadian cities because of its international flavour but this not mean becoming more important.
