Not being a Draco fan, I don't think he's important enough to be killed off. I've always got the feeling that Rowling created a not-too-bright, slightly annoying bully who just happens to hang around and antagonise the hero and ends up being turned into something bizzare and ridiculed. I know that his character might be explored and interpreted in quite a different manner, but I don't think that was Rowling's intentionn when she wrote him.

As to Snape, I wouldn't be surprised at his dying nor his turning out as having been evil all along. I like Snape, mind. But Rowling doesn't, and I somehow don't see her writing Snape as a heroic character at the end of the series.