Abortion, of which I'm pro, is already a step towards eugenics. In 200 years, many diseases will have ceased to exist because of this.
Down's Syndrome has already been reduced over 90% in Europe, and by about 70% in America. The American parents almost certainly include a number of hypocrites, since 44% of Americans think abortion should be illegal.
Down syndrome happens by change so it will not cease to exist in the future just by having abortions today.