As a series, I think Castlevania shouldn't limit itself to just Belmont's vs Dracula anymore.
We know there are a crap load of Belmont's that never had anything to do with Dracula, but they still had to train and learn to master the Vampire Killer. We also know that they hunt other monsters and evils. Why can't we see some of those stories?
We've seen creatures like Galamoth or people like Graham who try to destroy/take over/remake the world in their image. There have to be other evil cults out there who aren't devoted to Dracula. Where are these stories?
Lastly, we know the Belnades family has a history of fighting evils and working for a Church that doesn't acknowledge them officially, to save a humanity that persecutes them as witches. How cool of a story would it be to focus on one of them? There's also characters like Henry Oldrey, Cornell, and Shanoa. They have nothing to do with the Belmonts, and are barely connected to Dracula. I would love to see more characters like this also.
I guess what I'm saying is that when I see something labeled Castlevania, I know I'm going to see something that takes place in the CV universe. I love watching the different chapters of the Belmont's vs Dracula play out, but I also wouldn't mind exploring the CV universe beyond Dracula's castle.