How Did Jake Die?
There are a ton of rumers circling about this one, but here's a wild guess:
DID JAKE DIE FROM HAWKFROST?
I think that it is possible that Jake died from Hawkfrost because Hawkfrost wants revenge on Firestar, and while he was in the Dark Forest he could have learned about Jake, and have killed Jake by appering and killing him, or some other bad way. It's a long shot but he could have thought that since Firestar *cough* killed his father, then he should kill Firestar's father. I know I will be criticzied about this in the comments, but hey, you never know.