To put the Chief Justice's career in perspective, she was appointed to the Supreme Court in 1989.  Not only has every judge who was on the court when she joined it been replaced, but their replacements (and in some cases their replacements' replacements) have also been replaced.  She's a singular figure in the judiciary, the longest-serving Chief Justice, and one of the best -- if you compare her tenure to some of her predecessors, she was far better at locating consensus than the sometimes fractious courts in the years immediately after the Charter.

The next Chief Justice will, based on precedent, most likely be Justice Abella (the senior puisne justice has been appointed in all but four cases, and two of those were slightly modified seniority; only twice has seniority been thrown out entirely), while the new puisne justice, drawn from the West, will give Trudeau the opportunity to add greater diversity to the bench that he clearly wanted with the Atlantic seat but couldn't manage.