Earlier quoted context omitted.
Software isn't precisely zero-sum, but it's zero-sum assuming a static supply of companies to work for. Which ends up being the case in Canada, since 1. there isn't much of a culture of entrepreneurship; 2. there are few VCs, and they're pretty much all hyper-conservative, to the point that they may as well be banks.
Influx of immigrants, with zero shackling of immigrants == good chances of successful entrepreneurship. In a few months/years, students from India and China going to US for grad studies will slow down, and most of them chosing Canada over US. In a few years, if US continues its systematic and unfair ways of keeping citizens of India and China from immigrating to US, and Canada continues its policy of courting immigra…
Meanwhile, these startup founders often come back to Canada after getting their startup off the ground in the US... to create a Canadian "engineering branch office"—i.e., to hire tech talent at the cheaper Canadian going rate. But, of course, this only happens for startups that manage to get to a stage where they need whole offices of additional tech talent—which is not most startups.
Given this dynamic, I wouldn't expect increasing the number of available developers would do much at all. Now, if you could come up with some way to keep entrepreneurs from moving to the US, that might help...