I’ll add, the more interesting potential retirement is Thomas. He’s the senior justice on the Court at this point, and I remember hearing 15 years ago that he didn’t really like the job. I’m actually slightly surprised that he hasn’t retired yet.
Also, figure that Breyer will be the first to announce a retirement in 2021 if Biden wins. He’s 82 and has been on the Court since 1994 (second oldest justice and third in seniority).