I think because the decades of redlining, housing segregation, and disinvestment stunted the growth of a strong black middle class outside of some isolated pockets in places, the black migration you see out of Chicago, is more due to current financial and safety issues. As the city continues to gentrify, and the poor continually find their rent and taxes rise, you can't blame them for fleeing to suburbs to hopefully find more affordable housing, better schools, and a safer quality of life.

That said, I'm not sure what the quick solution to that is, considering it's taken 100+ years to sow the seeds of what we are seeing.