I find the central question interesting.
A World Without Down's Syndrome?
I would certainly answer yes to that question, same as I would for any chromosomal or genetic condition, or any other disease.
Are there really people who think the world is a better place for the existence of chromosomal abnormalities?
If a wand could be waved and there would be no more Down's, would we really choose not to wave it?
I think it says bad things about a society when we fail to provide properly and generously for our fellow citizens with disabilities and illnesses.
But to me it makes sense to aim for a situation where as few people as possible are sick or disabled.
I would love if we could eradicate and screen out Cystic Fibrosis. That doesn't mean I think the lives of people with CF are of less worth.
Just that I think most people would not choose a life that is likely to be shorter and beset by illness and hospital stays.
If genetic screening can prevent that, then I think there is a moral imperative to do it.
I don't believe there can ever be a moral imperative to have (or not have) a termination. I think that is an individual choice for each pregnant woman.
So we don't get to choose to eradicate or not.
But if we discover a way to eradicate without termination, if science finds the magic wand, will we really not wave it?