The game came out this year on early access and had 20 million sales on PC in early November, sold 1 million copies sold on Xbox in the first 48 hours and has over 30 million players between PC and Xbox.
With the game now being 1.0 on PC I think sales will stay consistent because most optimization issues have been addressed and they plan on adding new maps and modes to the game. On Xbox I think the game will have great legs and it looks like its getting weekly updates so it will continue to attract new players and keep old players coming. I also think that it will come to PS4 in 2018 and that will give the game a nice sales boost. It's 2017s best selling game and I think it will be 2018s best selling game.