He told Polish site Strefa Inwestorow that the developer has no plans for Geralt to make a comeback because The Witcher was envisaged as a trilogy, and the third game provided a definitive end to his story.
However, the company will "probably" make another game in the Witcher universe at some point to keep fans and investors happy. It sounds like there's nothing concrete in place but if it's not a definitive sequel we can probably expect some kind of spin-off with a new cast of characters.
He also spoke a little about his ambition for Cyberpunk 2077, the developer's next open-world RPG. Kiciński said it will be much bigger in scope than The Witcher 3, and that he hopes it will become more successful. It also sounds like the developer wants to add a lot of new features to its card game Gwent in 2018, having spent 2017 balancing the gameplay.