Netflix has confirmed via a line in a press release that "Castlevania Season 1, Part 1 Coming to Netflix in 2017". I don't believe that the online streaming service has released anything in the way of further info themselves, but the series producer, Adi Shankar has fleshed out the announcement a little, revealing Warren Ellis as the series' writer and adding "I personally guarantee that it will end the streak and be the western world’s first good video game adaptation".
As per Shankar's Facebook page:
Castlevania is a Netflix Original Series with Season 1 launching in 2017 and Season 2 in 2018. Furthermore, I personally guarantee that it will end the streak and be the western world’s first good video game adaptation.
P.S. A.V. Club, stop saying mean s*** about me.
P.S.S. Kevin Kolde is the man and Seasons 1 & 2 were written by Warren f'ing Ellis.
Warren Ellis, by the way, is known for writing comics including Transmetropolitan, The Authority, and Nextwave, as well as several novels.
There's another Facebook post from August 2015 which gives a bit more information about the intended direction of the show, although a lot can change in a year and a half so it might now be an upbeat quirky musical:
"Breaking News: I’m producing a super violent Castlevania mini-series with my homies Fred Seibert and Kevin Klonde. It’s going to be dark, satirical, and after a decade of propaganda it will flip the vampire sub-genre on its head."
Seibert founded Frederator Studios, by the way. Their stable of animated shows includes Adventure Time and, my personal favourite, The Fairly OddParents which feels really promising.
Anyway, what I'm getting from this is that it will be a cartoon show about upside-down vampires or "sǝɹᴉdɯɐʌ".
˙ǝɔuǝɹǝɟǝɹ ɟo ʇuᴉod uᴉɐɯ ɐ sɐ III ɐᴉuɐʌǝlʇsɐƆ sǝʇᴉɔ ʎllɐɔᴉɟᴉɔǝds ʇɔǝɾoɹd sᴉɥʇ puɐ pǝʌloʌuᴉ ʎllɐnsn ǝɹɐ sdᴉɥʍ plo ƃᴉq ˙ɐlnɔɐɹp ɥʇᴉʍ lɐǝp oʇ ʎɹʇ ʎǝɥʇ sɐ sʇuoɯlǝq ǝɥʇ pǝllɐɔ sɹǝʇunɥ ǝɹᴉdɯɐʌ ɟo ʎlᴉɯɐɟ ɐ punoɹɐ ǝʌloʌǝɹ oʇ spuǝʇ puɐ (ǝɯ ǝʞᴉl) sǝᴉʇɥƃᴉǝ ǝɥʇ uᴉ ʞɔɐq pǝʇnqǝp ɥɔᴉɥʍ ᴉɯɐuoʞ ʎq pǝdolǝʌǝp sǝᴉɹǝs ǝɯɐƃ ɐ sᴉ ɐᴉuɐʌǝlʇsɐƆ
Collider had a bit more information at the time thanks to a Q&A with Shankar. He referred to the goal of the project as being to bring "hard-hitting anime" to America and cited Akira, Ghost in the Shell, Ninja Scroll and Young Justice as influences.
I think the game franchise was actually intended for the big screen a few years back with a Dracula origins story as part of it but it's stalled for so long that I assumed it had been cancelled for good. Apparently people are still sort of circling the idea but there are rights issues and so on so it looks like this Netflix series is your best bet for a Castlevania project.