We will be able to modify our machinery ad hoc at any point in our lives. In fact, recent RNAi trials show that we can silence unwanted genes in humans at will.
I'll admit I haven't kept uptodate on this line of work. When I started uni (wow its alreay been over a decade) I was amazed at the beginning use of complimentary strands of RNA to bind to accessible parts of DNA to block expression. Is that the basic approach of those trials? I'd be interested at looking at any material that may be freely online.
I wouldn't say eugenics is obsolete though. Why not "enhance" the process itself. Think of the possibilities open to two people who love each other but who's genetic matching reveals their offsping could suffer from some horrible defects. I'm strongly for somatic gene therapy of the child because we should look after those of us alreay here. But I'd be thrilled with gene therapy correcting the germ line defects of the parents. Then their children's own germ lines should be rid of those deleterious alleles as well.