LA - blacks moved to riverside, victorville, the antelope valley etc.
NYC - blacks and puerto ricans went to numerous small cities and towns in the hudson valley and eastern pennsylvania ie "ghettos in the woods" as they are called. scranton is full of trash from the bronx, used to be all white.
Chicago - blacks from the demolished public housing around downtown went to smaller cities in illinois, indiana and iowa. joliet, des moines etc.
this process is a big part of the increase in mudsharking. blacks in downtown ghettos were high socially segerated from whites. when they move to iowa, they are now in school with whites, in white neighborhoods etc.
remember, gentrification is only really happening in a handfull of the biggest and richest cities. cities like milwaukee, cleveland and many others continue to get blacker and lose whites. even a city like philly has not had any real displacement of blacks yet.
blacks have only been pushed out of NYC, LA, SF, Oakland, Chitown and DC.