According to the latest news, it seems that it will be possible to complete cyberpunk 2077 without going through all the missions of the main storyline. The news came through an interview conducted by the Polish website Spider's Web, during which Pawel Sasko, head designer of the branded title CD Projekt RED, confirmed that it will be possible to finish the title even without completing the main quest:
We built the Cyberpunk structure based on our experience from The Witcher 3 [...] the main storyline will have several subplots surrounding it which will do something they have never done before: change the main storyline of the game in such a way that you may not not even finish the main storyline, but still finish the game and get a completely different ending than the game of another who has made different choices, met different characters and established relationships with them.
Sasko then specified that the story of Cyberpunk 2077 will be modeled according to our choices during the various missions, which could lead to an "anticipated" epilogue compared to the natural continuation of the plot. Some missions, in fact, will be exclusive to some specific narrative paths, which means that the story can develop in drastically different ways depending on the choices made.
As you will know by now, the title has undergone a new postponement of the release date. Initially scheduled for 16th April, Cyberpunk 2077 had been postponed to September 17th, but for the second time we were faced with a new release date: that is November 19 2020.
We have decided to postpone the launch of Cyberpunk 2077 from September 17th to November 19th.
Those of you who know our way of developing video games know well that we don't deliver something if it's not ready. "Hello what is finished" is not just a sentence that we say because it sounds good [...]
Finally, we remind you that the title will be made available on Google Stadia, PC, PlayStation 4, PlayStation 5, Xbox One and Xbox Series X.