I've repeatedly noted that arguments to abolish the death penalty because of the increased cost of litigation it engenders are tendentious. The activists who raise the expense of the death penalty by devoting waves of litigation (often subsidized by BigLaw pro bono programs) on behalf of convicts on death row aren't going to disappear if the death penalty does; they'll simply move their next target to the supposed unfairness of life without parole, and government penal systems will still face large legal expenses, just shifted to a different set of prisoners. If anything, the expenses might be larger because so many more prisoners have de jure or de facto life sentences, and the precedential effects would be greater.
Additional support for this hypothesis is now found in the European Union, where the "European Court of Human Rights has issued a disturbing ruling that life without parole is 'inhuman and degrading' treatment forbidden by Article 3 of the European Convention on Human Rights." [Bader]
Twenty years from now, how many justices will say that evolving standards of decency have changed the meaning of the Eighth Amendment in this regard? It really depends who gets appointed to the bench to replace the current justices.