As I stated at the time of the oral argument:
Based on the quantitative score-card nature of the "reasoning" that the Court displayed in Roper v. Simmons (where they ruled that since some states had stopped executing juvenile offenders, "evolving standards of decency" forbade other states from executing juveniles), the Court should affirm Kennedy's conviction since no states used to authorize executing child rapists and now 7 states do-- a "trend" towards authorizing executing these offenders that the Court, to be consistent, should find to be as much an "evolving standard of decency" as they found the contrary trend to be with respect to permitting execution of juveniles.
Why do I get the feeling that somehow the Court's liberals and the abolition lobby will move the goalposts?
Sure enough, in today's opinion, the majority manages to conclude that despite the trend towards authorizing death for child rape, there really is no consensus, apparently because not enough states have yet enacted such statutes. Yet as the dissent points out, it's hard for a strong consensus to develop when the states know the SCOTUS is ready to nullify whatever they enact.
Of course, this squelching of any emergent consensus is necessary "because, in the end, what matters is the Court’s 'own judgment' regarding 'the acceptability of the death penalty.'"
And needless to say, the majority has all kinds of philosophical, policy reasons it doesn't like execution of child rapists... too hard on the victim, not proportionate for the offense, not a deterrent, blah, blah, blah. All very interesting, I'm sure, but of no legal or constitutional significance.
And a little more of our self-governance and liberty disappears.