(I say this naive of all sorts of things, but...) I wish Canada would do something bold and actively court all these high-skill people who are probably interested in jumping ship. Make it easier for whole companies to move and bring their employees, make it easy for entrepreneurs to start a business serving this new migration, relax some tax rules for those in the process of moving, make it easy for extended family to tag along, make it clear it'll be easy for them to go back... ehh, and do something about housing.
Then, take out billboards in big cities. Put on events in the US. Partner with Canadian companies to handle logistics for potential employees, etc., etc.
Don't just go "Hey smart people, come to Canada" and afterwards say "I bet they'll do smart-people things!" Go for an unprecedented scale migration and actually shape the process for long-term benefit and payoff.
In the past I figured we didn't do this because we didn't want to piss off people in the US, but, I feel like who gives a shit now.