Castlevania has been coming out with new releases nearly yearly since its inception in '86, with thirty-something games under its belt. When I stop to think about that, it's the stuff of utter disbelief that a certain standard of quality has more or less been maintained throughout its entire existence. It's frankly miraculous the series hasn't stagnated beyond all redemption long since, though admittedly there have been dips into lethargic developments along the way, particularly as of late. Can it sustain itself anymore? Probably, with ingenuity and understanding of what makes it great, but I'm not sure if that is so readily apparent to the people involved with the series these days.
The last completely new Castlevania project was Lords in late 2010. A year and a half into it, this is almost as long as the world has ever went without Castlevania. I hope it's gone for more, and the time is taken to better the series, whether it is by letting it rest, developing new ideas, or fine-tuning old ones.
The only thing that slightly bothers me about the prospect of a long-term absence is the manner in which the series has seemingly bowed out with. Lords and Harmony of Despair at least to me represent two of the worst extremes Castlevania could aspire to, so there's not exactly a lot of happy association involved there. Something like Metroid could hibernate for eight years because a masterwork kept the fanbase content and hungry for more. Castlevania's current direction has attracted some new blood, but probably alienated just as much, if not even more.