It looks like a sequel to Bloodstained: Ritual of the Night is currently in the works.
Publisher 505 Games has confirmed in a Reddit post that developer Artplay is currently in very early planning stages for a sequel to Bloodstained: Ritual of the Night. Artplay is the development studio headed up by Castlevania veteran developer Koji Igarashi, and with the Castlevania: Symphony of the Night spiritual successor releasing back in 2019, its not surprising to discover that thoughts have turned towards the next game.
However, 505 Games confirms that currently, development resources are still focused on completing upcoming content for Bloodstained: Ritual of the Night, so it could be a long while until we see the sequel.
Bloodstained: Ritual of the Night is available now for Xbox One, PlayStation 4, Nintendo Switch, and PC.