Thank you for that very important and very interesting question as well.
The legal community has now produced enough renowned lawyers that we can envisage appointments to all courts, including the Supreme Court of Canada.
We have many francophone and francophile lawyers whose knowledge of French is excellent and who can engage in the kind of intellectual debate that takes place in the Supreme Court.
The objection that there aren't enough qualified francophones to head in that direction can be dismissed out of hand.