While you can generally expect very extensive games from CD Projekt, the upcoming 'Cyberpunk 2077' will be a bit shorter than 'The Witcher 3'.
This could apparently be learned at a recent Annual Community Event, which states that the core story should not be close to The Witcher 3 from a perimeter perspective. But the replay value should be a lot higher. Accurate numbers have probably but not mentioned.
"In terms of length, the main story of Cyberpunk 2077 could be a bit shorter than in The Witcher 3, but with a much higher replayability. At the same time, they did not measure the length of the entire game, just the main story and the main side quests. "
Furthermore, CD project has probably commented on the secondary tasks, which this time turn out to be more complex. In The Witcher, these were described as "single line", while the side missions of Cyberpunk 2077 can also affect the main and other side missions. Further details are not available.
Therefore, this information is not officially confirmed, even if they appear quite logical and describe a natural progression.
Cyberpunk 2077 will be released in April 2020.