Cross post from a Reddit post of mine but I've done some quick investigating on this after getting excited from the teaser.
As a big Castlevania nerd I'd like to point out that this looks like its based on Castlevania III, Sypha, Grant, and Alucard are all dead ringers for their more modern versions especially for Alucard wielding a sword in the teaser. This is exactly what I wanted to see for this series when it was first announced so my optimism has shot up, this is canonically the first Belmont to kill Dracula.
I've done some more digging and apparently the writer is Warren Ellis who is an English comic book writer and from some digging I've done he's been sitting on a script for a trilogy of Castlevania III movies since 2007. There's an old blog post from that year that has him talking about the specifics of the script and feeling like he'd need to cut Grant DeNasty from what was then a movie, but the teaser clearly has a knife throwing dude so that might have changed. Also in the blog post he name drops Lisa as being an important character which strikes me as him knowing the source material really well extending past Castlevania III. If anyone remembers in Symphony of the Night, the Succubus illusion is that of Lisa or Alucard's mother and Dracula's wife which in the lore is the whole reason he goes on his conquest across Europe is because of her burning at the stake if I'm remembering correctly, which is exactly the set up for Castlevania III or whatever this animated series looks like it will be covering.
https://www.bleedingcool.com/2017/0...is-wrote-castlevania-animation-ten-years-ago/
The knife dude is just Trevor, I think Grant's cut which makes the blog post hold more water as being the current plot for the series. Very excited for July now even still though.
tl;dr Castlevania nerd thinks it looks promising and might be very faithful to the game series.