That depends on which continent we're talking about.
If we're going with Japan, then I can easily see composers from Square-Enix or Capcom taking a stab at it. Case in point for Square, other than the aforementioned Uematsu, Yoko Shimomura can step in herself in a manner similar to how she provided music for Parasite Eve or LIVE-A-ヨVI」 (both the original and its remake). We could also take a stab at any of the main composers from Devil May Cry, considering their blends of atmospheric orchestral music and heavy metal.
For Europe, there's quite a few composers that can work out for this series. Allister Brimble for instance has done such work, especially with his professional work with chiptunes, like with Ghosts 'n Goblins on GBC. On top of that, he also did work with Konami for New International Track & Field on DS. There's also Peter Connelly, who worked on three of the Tomb Raider games, Tim Folin who is in a similar boat as Brimble for his chiptune work, and of course Grant Kirkhope of Banjo-Kazooie fame.
For the US, well the most obvious choices would be Tee Lopes and Jake Kaufman, due to their mixing of genres in their works. Ither than those two, I can see a few film composers involved in the series who can tie into the origins as an homage to the older monster movies that inspired Castlevania in the first place. The first two off the top of my head being Michael Giacchino (Medal of Honor, Jurassic Park, a good amount of Disney and Pixar films), Harry Gregson-Williams (Metal Gear series), and Danny Elfman (most of Tim Burton's works).
Of course let's not forget Chernabogue and the guys from OC Remix.