The Witcher 4 hasn't been announced, but it's an inevitability, and inevitably that will likely land on PS5, Xbox Series X, and PC sometime in the next 10 years or so. At the moment, CD Projekt Red is focused on Cyberpunk 2077, which is likely to steal its attention for awhile. However, after Cyberpunk 2077, its expansions, and its multiplayer add-on are done and dusted, you'd assume the Polish developer will return to the series that put it on the map, and the series that has only gotten bigger since The Witcher 3: Wild Hunt hit in 2015, thanks to The Witcher Netflix series starring Henry Cavill.
That said, for now, CD Projekt Red isn't talking about The Witcher 4, or whatever the next entry in the series winds up being called. However, it did recently talk about the series' future, or more specifically CD Projekt Red's story designer Jakub Szamalek did. Speaking to VG 24/7, Szamalek revealed that he has some regret that the team didn't get to explore Ciri as a character very much. However, he then teases that this may be rectified in the future.
"I regret we didn’t get to explore Ciri’s past a bit more," admitted Szamalek. "She’s such an amazingly rich and complex character. Due to obvious reasons – well, she’s pretty much gone for two-thirds of the game – she didn’t get quite as much screen time as we writers would have liked. But hey, maybe it’s something we’ll get to get back to in the future."
As you can see, Szamalek's language is a bit vague and non-committal here, but it does echo what other developers on the series have said in the past. It's easy to imagine the series continuing on with Ciri, but I doubt it will. While that may seem like a reasonable place to pick back up, the reality is Geralt is the face of the franchise, and the Netflix series is only amplifying this. You could make Ciri the next protagonist, but that's a bit risky. Geralt isn't iconic like Mario, but he's synonymous with the series and the more recognizable face and name. Besides, I don't think I'm ready to say goodbye to Geralt yet.