Sybill Trelawney may not always be able to see into the future, but she has prophesized the death of Voldermort;

The one with the power to vanquish the Dark Lord approaches. born to those who have thrice defied him, born as the seventh month dies, and the Dark Lord will mark him as his equal, but he will have power the Dark Lord knows not and either must die at the hand of the other for neither can live while the other survives. The one with the power to vanquish the Dark Lord will be born as the seventh month dies.

How do you think the Half-Blood Prince of Book 6 ties into this?