So we know that Witcher series has sold 25 million units in 2017. In 2016 the series had sold 20 million units. Witcher 3 was half of that. By that time Witcher 2 was five years old on PC and four year old on Xbox 360 so it probably had sold most of what it would sell lifetime. Witcher was eight years old so sales would be low after that. It is safe to consider that Witcher 3 has sold 15 million units. Also five million of those sales were in the last seven months which is incredible for a game not made by Rockstar and Nintendo.
Do you think the legs of this game are impressive? Can Horizon have these kind of legs? Also this makes me curious about Bloodborne, another highly rated game in 2015 for which the last sales figures were given in Spetember 2015 when it ha sold 2 million units. Since then we got an expansion and a Game of the Year edition for the game and according to this site Bloodborne is always in the top seventy five best selling game of every week, so it could have sold over 3 million units by now.
https://www.cdprojekt.com/en/media/news/cd-projekt-posts-strong-results-2016/
http://www.dsogaming.com/news/the-witcher-3-wild-hunt-has-sold-near-to-10-million-copies-worldwide/