The Ending

We don't find out if the Baron dies or not. I'm assuming he and Stefan die, but they really just sort of disappear.

Ilsa blows her hand at the end to help wrap up the plot by telling the Baron that she wants him to take his life like he took hers and let his own hand destroy him. Then she really blows it by telling him that his unholy sin gave her over to the dark powers, but by giving his immortal soul to them, she will be free, ERIC. So then the Baron tries to stop the flooding of the crypt and so he is trying to prevent his own death, thus invalidating Ilsa's scheme.

There are several shots interspersed after Stefan arrives where Ilsa is in the water with Stefan and a man with his back to the camera who has a full head of black hair and different clothes than the Baron. Then we see the Baron again in the water with his eyes closed.

By the time Andre shows up, the Baron and Stefan have vanished under water. So I guess the Baron dies but he has not committed the one unpardonable sin in the eyes of God, thus saving his soul!