Cyberpunk 2077 (opens in new tab)'s main storyline and major side quests will be "a little shorter" than The Witcher 3 (opens in new tab), according to a Reddit user's account (opens in new tab) of a Q&A with the CD Projekt Red team. User u/shavod writes that the developers believe the main story will be a little shorter than The Witcher 3, but the game will have "much higher replayability" than the developer's last blockbuster title.
Despite this, the devs claim to have only added up the main storyline and major side quests, not "all the encounters and smaller quests", which are currently unaccounted for. So, as far as completionists go, the entire length of the game and how it compares to The Witcher 3 is still unknown - it's still entirely possible that a 100% run Cyberpunk 2077 ends up being longer than The Witcher 3 (not including those two massive DLCs).
The structure of Cyberpunk 2077's side quests are a direct reason why the replayability is so high - devs likened The Witcher 3's quest structure to "a single line, with a bunch of branches sticking out of it", while Cyberpunk 2077's "branches grow more branches, which then often tie around each other." So one sidequest can become another sidequest which will likely impact other sidequests, and many of them tie into the main storyline, likely in much more complex ways than in The Witcher 3. This means that you could play through Cyberpunk 2077 and miss some of the extra branches while still completing the game - if that ain't replayable, I don't know what is.
Cyberpunk 2077 will drop on PC, Xbox One, PS4, and Google Stadia on April 16, 2020. As GamesRadar+ previously reported (opens in new tab), the Cyberpunk 2077 won't be on PS5 or Xbox Project SCarlett when they launch.
You don't need to complete any side quests to get in on these Black Friday game deals (opens in new tab).