Cyberpunk 2077's expansion Phantom Liberty offers fans a great additional story, featuring Idris Elba, a new area to explore, and more, but it doesn't interfere with the events of the main quest, nor does it take place canonically after the game's ending.
Speaking with PC Gamer, narrative director Igor Sarzyński explained the reasoning behind this. "We did consider a couple of other scenarios," he said. "But none of them were a continuation of the main game story. The endings are too diverse to have a single post-main story thread make sense for them all—and you don't want to pick one and invalidate other people's choices."
"The endings are written as we wanted them—leaving players with an uneasy feeling, forcing them to think, not providing straight answers," Sarzyński continued. "They stick with you. No need to water them down. Sometimes less is more."
The game does add another potential ending if you want to pursue it, but it comes at a great cost. Again, it seemed CD Projekt Red didn't want to have good and bad endings. Rather, it wanted you to be left with a mixed feeling by the time the credits rolled.