According to CD Projekt Red, by developing The Witcher 3, they now have more experience in creating large size game. Since they did reveal that the new Cyberpunk 2077 is going to be a lot bigger than the Witcher 3, we are going to guess that they experience with the Witcher 3 is going to help speed up the developing process but how fast are we talking about.
If the game was to be as big as the Witcher 3, we would expect them to use less time to create the new Cyberpunk 2077 game but since the game is much larger, we would be lucky if the game even made it out by 2017.
The game is also very different from the Witcher 3. Unlike the Witcher 3, Cyberpunk 2077 is set in a distant future which means they will have to make it from scratch. There were rumors about the game arriving later this year but we think that is highly unlikely.