Roberts isn't nearly as conservative as the current other 3 conservatives and seems to care about court legitimacy. I think he will continue to be a moderating voice that limits how far right the court will go.

Likewise Thomas isn't in the best health and getting up there in age statistically for a black man.

There's also the fact that historically speaking, the Supreme Court has actually reflected public opinion pretty well. The courts have been more restrained when public opinion is firmly against something. Some of that is fear of nonimplementation, but also the threat that new legislation will be implemented. So say the Supreme Court decided to make abortion a state issue. The backlash would be significant. Yes that has significant impact short term in many states, but it would prompt more people to vote and push for legalization. Not ideal, not a permanent position either.

Then there's the less rosy outlook where Ginsberg or Breyer retire. That would be worse, but I don't think either would step down under a Trump presidency. And I'm pretty sure Ginsberg would smack death in the face. Sure she's 85, but it's a badass 85.