I think there are just two possibilities for Draco on book 7th:

1-He dies. Voldemort doesn't want him anymore, he's not strong enough, he could not kill Dumbledore. He is not usefull anymore, and He (must not be named) is angry with his father because of the things that happened at the Ministry. And that will be a good point on the book. The bad ones have to die or become good ones...

2-He turns out to be good. He maybe couldn't really kill Dumbledore because deep in his heart he knew he wasn't a killer. Maybe he will realize that what Voldemort is doing is not the kind of person he wants to be, even if he has always says so. Do you think he really wants to kill Hermione?

Do you imagine Draco becoming good at the last minute, and giving his life to save Harry from Voldemort?

That would a great end !!!!!