According to this article, recent figures from Invest Quebec show Montreal's game development workforce has grown by 177% in the last 2 years. We're 47 heads short of the 5,000 mark. Awesome.
I don't know what the numbers were when I moved here six and a half years ago, but I was (just over) employee 1000 at Ubi Montreal and there were less than 500 of us in the studio when I arrived. Probably the Montreal dev community was less than 2000 back then.
We're still not at the size of the dev community in Vancouver or the Bay Area, but with 5000 of us, and with so many major publishers launching new internal development studios, if we can maintain levels of growth anywhere near this for another couple years, we'll be the largest game development area in the world easily I imagine.