It will never work for them. Simple numbers dictate that fact. The current population numbers of black and latin Americans, and their sizable influence of economic power, is much more powerful now than in the past.
But there is now another factor that also has more influence than in the past. Mixed race Americans, of black and white, and latin and white families.
All of these populations of people can greatly influence economies in counties and cities in every state, which redistricting won't protect Republicans in state and local elections. Which is how political power can be changed far more rapidly, than in national elections.