It's one step forward to full abolition. I wonder when we'll get to 20 or even 25 states without the death penalty. It's not impossible to see a scenario over the next 10-20 years where the Supreme Court takes up the death penalty in and of itself in light of that and its "evolving standards of decency" test. Justice Kennedy probably wouldn't pull that trigger, but I could see a liberal majority do so. A liberal majority on the Supreme Court is probably the only way we'll see full abolition of capital punishment in the United States (and I mean something like the Brennan/Marshall opinions and not the Furman decision).
I'm sure there are votes on the current Court that agree with Justices Brennan and Marshall, but just do not take their hardline position (in that they would always object to the imposition of the death penalty). Even Justice Stevens in the lethal injection case didn't go that far, despite his position that the death penalty itself was in violation of the Eighth Amendment. As I understand it, the conservative majority on the Court during the 80's would take up death penalty cases in response to those two in order to uphold them and thus hasten executions. If there were a fifth persuadable Justice on the Court, I have little doubt that the four liberal Justices would strike down the death penalty in all cases.
The SCOTUS is indeed the only plausible way for abolishing the capital punishment. Even if (a very big "if") the Congress votes to scrap the federal death penalty, it wouldn't affect state laws and for sure there will be some states, even with a strong nationwide trend against the death penalty, to retain in and execute sentences.
The only theoretical way for a nationwide abolition without the SCOTUS delivering a judicial ruling is a constitutional amendment. Very unlikely as well.
