Harry and Cho won't get back together, I don't think. Rowling wouldn't have said that Harry was thinking that the ways he tried to impress her, yadda yadda, in the past, were no longer part of him, if he was eventually going to get back together with Cho. He could just be in a slump over Sirius' death--but I doubt it.
Seriously, though, why did she have to go and kill off the coolest character, my most favoritest since book 3?!?! I cried and cried after his death and til the end, then cried after I finished it. He was so great. I think we'll see him in the future though--whether in some kind of memory or another way--theres' too much to him to never have him in the books again, but nothing cheesy and dumb like as a ghost.
Like someone else said, I thin kthe realtionship between Harry and Lupin will deepen in the future. He hasn't got parents, now Sirius is dead *stops to bawl for a few moments*, so the closest thing he's got is Lupin, or, well, Dumbledore, but he likes to keep himself at a fair distance till he finds it necessary, ya kow?
I think this was my favorite of all of the books, the 3rd coming in as a close second. It was a lot darker, and I think that's really what made it so interesting. It was good to see Harry with so much more depth and humanity.
I think maybe there may be a fight between Harry and Ron over becoming the Quidditch captain in the next book. It seems like they both have a good shot at it, and it might have some depth.
Ron and Hermione won't get together. That'll make things too complicated, and, seriously, there's never been literal romantic tension between them, as far as I can remember. There just friends, and nothing else. Besides, if they got together, that would leave Harry as the "third wheel", and that would be really weird. I don't think Harry and Ginny will get together either, she's attracting too many guys and clearly doesn't think of Harry that way anymore, and even though she's much more brave, mature, smart, and respectable character now, I think she'll always have that "Ron's little sister" thing going for her when it comes to how Harry looks at her.
I also think more of a relationship--or somek ind of plot development--will happen between Snape and Harry now. Harry will probably learn to come and trust him more, even though he may not be willing to all the time.
Grawl or however you spell his name will have an important part in the next book--Rowling wouldn't have included him in the fifth book for such a small part if she didn't have more reasons for him.
I also think Fred and George will get involved in some kind of plot twist that has to do with the dark going-ons of Voldemort, even though they may not want to.
The Death-Eaters will probably be out of Azkaban in the next book. I also think Voldemort will manage to lure someone good that we least expect over to his side in book 6--someone that'll be a powerful tool for him, too.
Okay, that was my two knuts--or maybe more than two, looking at the length of what I wrote! 🙂