Good ideas, Flygal101...
I think that there could be another prophecy in "Half-Blood Prince" or Book Seven. Dumbledore was very insistant that Professor Trelawney stay at Hogwarts even when she was out of a job, which makes me think he expects she will make another prediction. Since she has been known to make two prophecies related to Voldemort, I can see why Dumbledore wouldn't want her to leave Hogwarts... what if the next person to whom she made a prophecy were a Death Eater?
Talking of Professor Trelawney...
Do you think that she and Firenze will teach Divination together in "Half-Blood Prince"? And do you think that Harry and Ron will continue to take Divination? I know that there are many theories out there that they are Seers based on some of their "made-up" predictions in "Goblet of Fire."
Whether there is another prophecy or not, we are definitely not finished with unfogging the future!
I don't think there will necessarily be another ball, but J.K. Rowling has made it clear that there will be more romance in the coming books. And by the way, do you think there is some special event for Hogwarts graduation? Between Percy, Fred, and George, I would have thought that such an event would have been mentioned by now if it really existed, but you never know.