Sacrificed in a sex ritual: Since we see a scene with a player character and Wyll playing in the background, while the writer speaks about our Tav being sacrificed, I think it's Mizora who would sacrifice Wyll and our Tav. Are these succubi in the background?

Turn you into a vampire: I think there is not much choice - Astarion, if he becomes a true vampire. Although I don't think he necessarily wants to become one. When asked if he would need to drink Cazador's blood to become a true vampire, he says something along the lines of: in theory yes, but that he would settle for killing Cazador, to be free from him.
I don't think Cazador would turn our character into a true vampire, but I wonder what would happen if Cazador turns us into a vampire spawn: would we still be able to kill him with the other companions, or would this be a Game Over moment?
(I hope there will be an epic fight, Tav & the party vs. Cazador)

Marry: who knows - maybe all of them?

(I must admit that I am hoping for some kind of happily ever after for my characters and their partner.)