Official statement from CD Project Red:
To polish and improve the game so it's 100% complete is the right reason to delay any game, but this is starting to get a bit ridiculous. This is why games shouldn't announce release dates so early. Any number of things can happen between those announments and said release dates. There has to be a point where gamers need to stop forgiving developers/publishers for these delays and start asking them if they knew it wouldn't be ready in time, why did you make that announcement and start taking pre-orders a so may long ago? For me, that time is now.