Low social mobility equals success

At Gene Expression, Razib Khan writes:

[T]he logical end point of a quasi-”blank slate” policy position is the diminution of environmental impacts so that only genes matter

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If it turns out that the heritability of intelligence is relatively high in the developed world, then it may be that the Left-progressive project of ameliorating class based differences in access to cognitively enhancing environments has succeeded to a large extent. Barring genetic engineering this is the “end of history” for this project. It is a matter of when, not if (i.e., if you reject that the project has hit sharply diminishing marginal returns, logically it should at some point if the Left-progressive project succeeds). Assortative mating and more transparent meritocracy should allow for cleaner sorting within the population, and inter-generational class churn should decrease and stabilize at a basal level dictated by the random environmental variables which no amount of social engineering can squeeze out of the system.** A perfect meritocracy would replace cultural class with biological caste.******

A decrease in social mobility would signify the project’s success. I expect this contrasts with one of the primary measures of success for those who hold the blank slate policy position. Will they use an indicator of their success to argue that opportunity (in an environmental sense) is becoming less equal?