Stephen Breyer is 82 years old.
Sonia Sotomayor is 66 years old and has had issues with type 1 diabetes.
I'm not wishing ill on anybody here, but the truth is that time catches up to everybody at some point. And out of our current Justices, there are two (that just so happen to be liberal) that are facing their impending retirement.
Breyer and Sotomayor are a risk for the Left, yeah. But once the story of Roberts' extortion comes out, and that Kagan was the conduit for it, there might be no liberal justices left on the Court!
One can dream...
And Thomas could retire (i don't want him to!).
In the absolute best case Trump could end up with a 9-0 Court where 8 of the Justices are his appointees!! I dream of this.