Do you mean if they didn't have children and neither did anyone else? Well, in that case we wouldn't be here having this conversation. And if you mean just them, then I guess it will be a bit sad that we have a large percentage of a generation that doesn't have kids, but I also think it'd do a few small wonders for our planet. You know, with over-population and all....
Really, though, it won't be too long before there's few people left who were there. What, 40 years? That's sad.