If Republicans can get their act together
Economic collapse, and if Republicans remain reactionary post realignment
Good map! But why does Illinois vote to the right of PA and MI?
I am anticipating a Republican rebound in California, Illinois, and New York very quickly once it becomes "safe" to do so, e.g. Republicans secularize. While California and new York may come out of that slightly more swingy than current Texas, Cook county's depopulation is more likely to push it over the edge.
Of course the trends can reverse themselves, so feel free to correct me if I am wrong.
Speaking candidly about California however, Republicans may have burned too many bridges, so that may cancel out some of the depolarization post realignment.