There were several plans to remove slaves to abroad even before Lincoln came into office.
As the abolition movement gained strength, even in the 1840's, there was great concern about what to do with all of these people. No one really wanted them just freed to be delt with here. All could see the logistics nightmare that would arise, not to mention, the inability of being able to deal with the numbers discussed.
It was a real nightmare for all.
Not all were black that they were concerned with. All plans ran aginst the grain of the Constitution.
Blessings