I am finishing a big important part of a thing today, and it has been necessary to listen to [the Castlevania Netflix OST] ... in order to do it. Trevor Morris – @morristrevor on Twitter – wherever you are, thank you again.
Since Warren Ellis is the writer behind Netflix Castlevania I'm just going to assume that he was using the music as inspiration for when writing Season 3 of the show. Trevor Morris composed the music for the show.
Although time travel always makes a storyline messy, I would squee with delight if we get even just a few brief appearances of Saint Germain. Being a time traveller he could easily be a "foreshadowing tool" for events that may transpire hundreds of years later, in what would presumably be season 4 and onward.
Presuming Season 3 covers the entirety of the Curse of Darkness storyline and ends the Trevor Belmont era, I wonder how the studio is planning on doing the future seasons (if they get renewed for them). As I can't imagine them adapting every single canonical Belmont/game protagonist, since that would likely be far too many seasons the studio can reliably bet on for renewal, plus the repetitiveness of many of the games storylines doesn't lend itself to serial storytelling (it would especially reduce the significance of Dracula's death, if he keeps on being resurrected again and again).
I think the best route narrative-wise for future seasons, would be to adapt the Richter Belmont era and Soma Cruz era games with Alucard acting and the connecting thread character for a good thematic narrative trilogy of Belmont eras.