Re: "Therefore, assuming the powers-that-be would be willing to do so, in a super-high-tech regime several billion unproductive people could be supported in one or more tolerably dense enclaves at a relatively low opportunity cost. The real questions are whether the will to do so will exist, what troubles might ensue during the transition, and whether these unproductive billions will be able to form a tolerably functional society."

Organic humans becoming functionally redundant is likely to be the beginning of the end for them. They may well be able to persist for a while as useless parasites on an engineered society - but any ultimate hope for becoming something other than entities of historical interest would appear to lie with integration into that society - and that would take a considerable amount of "adjustment".