So based on this video, Marcin Iwiński confirms that Cyberpunk 2077 [at the time, it was referred to as "Cyberpunk game/RPG"] was in development prior to 2012 - since this CD Projekt Red Summer Conference took place May 30th, 2012. Here is his quote from the beginning of the video:
All of that is at the very beginning of the video and it's a very entertaining watch and might be new to many of you:Marcin Iwiński said:"Until not so long ago, we only had one team; but I'm really pleased to announce that since quite some time, we have a second team and I'm talking about it for the first time today - and the second team is based on Witcher dev veterans, so these are really seasoned developers. The guys who were working on The Witcher 1 and The Witcher 2 - actually they have been working quite a few years - if you gather all the nights they spent at the office working on this, it would be a few real-time years that they have spent on this project - they are really seasoned developer's and they're working on a new, AAA RPG. So I suppose you'd like to find out about what RPG it is [...] a Cyberpunk game; but not just a regular Cyberpunk game, on "The" Cyberpunk game - that's really important to stress."