Not neccessarily in the next book, but I think that Creepy Creavey will become this generation's Peter Pettigrew. He'll turn over Harry to Voldemort, Pettigrew will repay his debt to Harry by saving Harry's life and sacrificing his own. I think Dumbledore will die and this will be when Harry has to choose his own path of good (The side of the Phoenix) or bad (the side of Voldemort).

I don't think we've seen the end of Percy either, someone with his ambition can't stay on the straight and narrow. Percy is very ambitious, and Voldemort (maybe through someone else) will provide him with the easy path to success. The 16th July is not that far away.

The problem is that there are too many loose ends at the moment and there are two books to go before we get the final resolution.