Unfortunately, as best I can tell, JKR has NO plans for more HP after Book 7. Most recently she did an interview (which I read in its entirety on an HP fansite) on Saturday, saying she absolutely was not doing any more HP. She has previously ruled out the prequel idea, saying she did not want to do it a la Star Wars. (LOL, with all the parallels drawn there!)
I am not opposed to the "Snape is still good" theory, would make me much happier than I am now. I DO believe DD is dead, though I feel certain that in some way he will still be able to help Harry, even if it is only in preparation. I, too, noticed the flame incident at the funeral, and thought of the phoenix. And I also wonder where Fawkes has gone. Maybe to the OotP Headquarters? After all, he was used as a messenger... So perhaps we will see him again.
I'm happy with all the relationships, and hope that somehow Harry and Ginny will work out, though if he dies in 7, guess it wouldn't much matter! There is bound to be something of interest in Godric's Hollow. There has been speculation before about Godric being Gryffindor's first name, thereby making Godric's Hollow more than just the place Harry's parents died.
As for the book itself, I personally found it much more readable and enjoyable than OotP. And that is spoken not just as a fan, but also as a holder of a degree in English! JKR has said herself that she felt she rambled on too much in OotP, and I agreed with that assessment. On the other hand, HBP was a bit more predictable (in some ways) than I would have thought. I had figured out early on that Snape was the HBP. As to the books being too old for him or any of Harry's parents' friends...hello! This is 20+ years later than their days in school, and they're *still* using the same textbook! I'm also not surprised by DD's death, because we all know that in the end, Harry must face Voldemort one-on-one. I'm just hoping there are not too many casualties along the way!
BTW~Go Tonks!!