They already made a Symphony of the Night 2.
It was called Aria of Sorrow.
While there might be ways with a next-gen system to make something a more impressive and official "SotN 2," I agree in suggesting titles like Aria of Sorrow, Dawn of Sorrow, Circle of the Moon, Harmony of Dissonance, Harmony of Despair, Portrait of Ruin, and Order of Ecclesia as spiritual follow-ups to Symphony of the Night. That's honestly your best bet, as Castlevania is being led in a new direction.
And while SotN was and is popular, there are other Castlevania games out there that are a lot of fun, and some fans hold them in higher regard. Circa 1997-mid-2000s, most wanted nothing more than SotN 2, and the media still seems to hold that sentiment.
I'd like a return to the Nintendo 64 style with modern HD resources for at least 1 game, and at least 1 new HD hybrid of Castlevania III and IV, but I know that those are just as unlikely. We all have to deal with it in our own ways, and I wish you luck.