The thing with necromancers, being dead does not mean they are gone.

They might not be able to restore the rcv, but I could see an effort to some how reclaim their lost power. As former rcv, the Eebs could have a claim to it. The same could be said for Maggie, she was the child of a Demi rcv. How many people have such a blood connection.

I kinda wondered if the warden or winter knight some how claimed that power, in the act of killing the rcv. The winter knight could be seen as a representative of the winter court.

Simon was said to be the council expert on the vampire courts, so I bet that his lore is very valuable. I wondered if there was something unique about the vampire courts. Somehow these seven predatory races, each got a place on the accords. While different, these seven races see each other as some kind of extended kin. I always believed that implied some kind of common origin. My bet is they are each the result of magical creation or outsider influence.
Due to mavra and the kemmler book, I suspect we will see a lot of the BCV in the end. I bet Simon lore on them, would be very useful. We also know there will be a lot of power plays with the Wcv, so their lore would be seen. The rest of the lore could just be used to leverage the remaining vampire courts into the conflict.

 I wonder if Harry might have the protection needed to deal with such entities, now he is warden. The well could contain the entities, and eventually they could be forgotten. The description of those creature Thomas is against, sounds similar to the inmates of the well.

In some stories, necromantic arts could be used in a form of healing. Healing here is very advanced magics, I bet kemmler would be capable of a form of necromancy that could be mistaken for healing.

Names have power, faith a girl who believes in the power of magic and in Harry the wizard.

I could see the Wcv considering the remaining BCV as a loose end that need to be dealt with. If the remaining elders are somehow drawn out and removed, then what remains would be easily dealt with.