The Black rooster has Extended Black. That’s the strongest color to start painting the canvas of how a chicken will look. But there are two different genes that can turn a chicken solid white, either Recessive White or Dominant White. Those act differently. I don’t know which of these a White Orpington would have.
If it is Recessive White you will get all black chicks. The Recessive white will turn any chicken solid white if both genes at that gene pair match up but it has no effect if only one of those genes is present.
Dominant white will turn any black feathers white whether it is paired up at that gene pair or not. Since any chicks from that cross will have an Extended Black gene and a Dominant White gene, you will get all white chicks.
So either all white or all black. I don't know which.