Despite the fact that blacks had been freed from slavery they are still too important to the economy. They are still doing most of the menial labor so I do not really see a scenario where they are resettled anywhere. The only way something like that could happen would be if a really radical pro-black faction takes control of the federal government after the Civil War. Perhaps if the group that killed Lincoln had succeeded in killing everyone on their hit list?!? The radicals now in power could force the south, and any other part of the country that does not want to participate, into true equality for African-Americans. No segregation, no "Jim Crow" laws, forced integration in schools, employment, etc, all enforced by "Yankee" bayonets. Such a scenario would probably lead to armed resistance, and not just in the South. Once that gets settled you would probably see the rise of a strong "let's get rid of them" movement, however it would probably be a back to Africa movement, possibly to Liberia. The bottom line is that it would take something really extraordinary for any kind of reservation idea to happen.