The revelation on priesthood meant more than we realize, as did the revelation to Peter that the Gentiles could be baptized into the true church.
The revelation that the priesthood could go to blacks didn't just give the priesthood to those then living. It opened it to them over the whole course of the earth's history through temple work.
It was just like the door to missionary work being opened up by Christ in the spirit world.
When Peter received a revelation about the gentiles, it didn't just open the doors to gentiles here
on earth. It was God opening the door to the gentiles of all ages, as all who ever lived could then receive the gospel through baptism whether here or in the spirit world. That is because even those in the spirit world could now receive the ordinance of baptism, and could now get the gift of the Holy Ghost through temple work done by their righteous descendants.