DW speaking: (He makes me say that)
First of all, I don't think she would kill off Ginny and Harry. The main theme of this book is that love is the strongest magic. I actually think that the combination of Harry and Ginny with Ron and Hermione is part of the point.
The entire series (I didn't understand this until reading the 6th book) shows the parallels between Harry and Voldemort. They have similar backgrounds, but Harry came through it with an great capacity for love, while V came through it with none. That's the whole point. Harry will surviive because of the love of his parents, his friends, Sirius, Dumbledore, and all the others whose lives he has touched.