This is my assumption.
Since CD Projekt Red will be attending E3 this year, it would be unwise if they did not announce a release date during that time period. I mean, come on, 2 E3s without a release date would be ridiculous. If the game is that far off, then they should just not attend this year's E3 at all.
Games usually get their release date a few months prior to the actual release, so if a release date for Cyberpunk 2077 is announced, then it would be safe to assume that the game is only a few months off to be released. This concludes that the game will be released around late 2019, which would be October to December.
Now, the median of those three months is November, so let's say that the game will be releasing in the month of November. This makes the window of release to November 2019.
November has 4 weeks, so the median of those 4 weeks would be the second week. This shortens the release window even further, which means that the game could get released anywhere between November 10 to November 16.
Assuming that the game will release on a Tuesday like The Witcher 3 and many other games, this allows us to further the date even more. As a result, this gives an exact date of November 12, 2019.
However, that is too specific to assume, as the game could also get released on another week of November. Due to that, let's add another date just to be on the safe side: November 19. The game could get released on either of those 2 weeks, and a release in the first or last week of November is unlikely.
Speculated release dates: November 12 and 19, 2019.
*drops mic