In vampire lore theres no such things as harems right? Basically just open relationship type things with Sires and Thralls? I would assume that since vampires are immortal it would be pretty hard to only have sex with one person for the rest of your life.
Well, even if you are immortal and you are monogamous, people do change partners. Humans do it several times in their limited lifespan, I would assume it is even more understandable if you live a couple of centuries.
More in general, you can have any vampire lore however you want. Dracula in the Van Hellsing movie has 3 wifes, which would suffice as harem if you want. In the manga/anime Rosaria+Vampire, the main character is in a situation in which a vampire is part of his "anime harem". On the other hand, in pathetic Twilight there is a high focus on "ideal/perfect" partners.
The settings I mentioned are kind of joke, low quality settings if you will, but nonetheless are part of the vampire lore. So I see no reason why to assume one way or the other, more like you need to look into the specific setting. I am not the most versed member on this thread about VTM, but I would assume that anything goes there too..
Now, if you are asking whether this novel would go towards a harem or not, we really don't know. I don't remember seeing harems in any of Ptolemy's stories, although there were some more than two people relationships.
My personal take is that a situation revolving around MC being the main interest of several of the girls without being a stupid "we are so glad to share you with everybody, oh dear owner of Dracula's powerful cock" would be the most likely candidate. After all, the novel seems to focus on different characters having their own agenda. The current situation with Sharon, Laurie, Calisto and potentially Carmen seems to fit that description. Dream girl situation does not currently apply without further notice.