A Polish investor report on Stockwatch has estimated the release date for CD Projekt Red's Cyberpunk 2077 for the fourth quarter of 2019. So, sometime between January 1st and March 31st, 2020. CD Projekt has been quiet about the game and has not released any official information regarding its release window. The Stockwatch report appears to come from stock analysts and focuses on CD Projekt as a whole and includes information on the developer's other games.
Which is to say, this is an educated guess by analysts at an investment firm, and not a report put out by CD Projekt themselves.
The investor report made the rounds on the Cyberpunk 2077 subreddit where it was picked up and translated by Redditor Dr4kun:
Translation (a native polish speaker and a translator, but please take it with a grain of salt):
Cyberpunk 2077 vs RDR2: We're keeping to the estimation of a debut in Q4 of 2019, with sales of 19 million copies in Q4 alone, and income of 1.9 billion PLN (about 525 million USD). During a conference call, the Board has confirmed that quality remains the absolute highest priority for CD Projekt, and Cyberpunk 2077 will be no less elaborate and polished than RDR2. For comparison, the sales of RDR2 (gross) was 725 million USD within the first three days after it shipped, 15 million copies within the first eight days, and 17 million copies within the first twelve days (data from Take Two). The game was released only on PS4 and Xbox One consoles. With that in mind, our forecasts for CP2077 seem very reserved – remember the game will be simultaneously both on the consoles [PS4 and XBO] and PC. We also believe that the world of Cyberpunk / sci-fi should be more popular among gamers than the Wild West.
Now, this could very well be an accurate read on the release date for Cyberpunk 2077, and given recent game trends, we wouldn't be surprised to find out that the game is set to release at the end of fiscal year 2019 as opposed to the calendar year. February and March have become popular dumping grounds for games that get delayed or held up in development and miss the primary release window of August – November. However, because this is a report taken from an external investment firm, you will want to take this one with a grain of salt.