The Witcher 4 is the "most advanced" project of all the games that CD Projekt Red (and its partners) are working on right now.
That's according to Pawel Sasko, associate game director on the Cyberpunk 2077 sequel. Speaking on the Flow Games podcast, Sasko wasn't able to give much detail on any of the upcoming CD Projekt Red games, but he did give a rundown of the whole bunch, explaining that The Witcher 4 is by far the furthest along.
