As it stands now, I doubt that many American programmers would be willing to take the pay cut they'd have to accept if they came to work here.
I like it here, and I'm happy with what I make, but when you factor in the exchange rate, a typical US developer would take a huge salary haircut working here; probably 40-50%.
That is true. But there are also a number of perks such as universal health care. So maybe just a certain type of developer would move - one motivated by values rather than money. Perhaps similar to the draft dodgers who came up in the late 60s.
Sure, but (depending on the area, at least) you can live very comfortably on 50% of what a west-coast US developer makes. Techies tend to forget that our pay rates are way above the national average.