If were Justices Kavanaugh or Coney Barret I'd be screaming at Roberts now for throwing them and the whole "conservative" side of the court into the trash heap. When the court is packed, their opinions won't be worth sh1t. Neither will their careers.
I think that all of the justices are unhappy with the prospect of court packing and term limits. Breyer was not supportive of the idea, and the left attacked him. But to your point, the new justices could be deeply angered at Roberts for potentially throwing their future away. So far, the court is safe because Pelosi isn't on board with court packing. She is only supporting the President's commission to study the issue at this time.