The recent case of Chevron U.S.A., Inc. v. Natural Resources Defense Council pretty much transferred much of the massive workload now being done by administrative/regulatory agencies onto the backs of Federal judges.
Many of those case will dribble up to SCOTUS.
SCOTUS does not have the horsepower to handle the mess it just created.
Congress organizes SCOTUS - yes, it is Congress that defines much the range of SCOTUS jurisdiction and administrative things, like the number of Justices.
So it is now quite incumbent on Congress, even if we exclude concerns about bias, to restructure our Supreme Court. I have proposed a two tier structure - much like the Fed Appeals courts - and more Justices. We could even remove the title "Chief Justice" (thus really ticking off Roberts) and call it "Manager of Judicial Functions" or similar bureaucratic sounding term.