Heart of Stone, the first real expansion for The Witcher 3: Wild Hunt (not counting the 16 free drops of DLC) Heart of Stone may be closer to its launch than many have feared. At the PAX Prime expo one of developer from CD Projekt Red, Travis Currit, was attending, and he made sure to comment that the expansion is "almost ready, and shaping up really nicely."
Of course, "almost ready" is a relative term, but we take this as a good sign for making the suggested release window of October this year.
Content-wise the expansion will offer a roughly ten hour story. It's the first of two planned expansions, the other being Blood and Wine, and together they will offer 30 hours of new content and a vast new region called Toussaint.
That region will not be ready until the 2nd expansion however, as Heart of Stone is set to No Man's Land and the roads and alleys of Oxenfurt. With ten hours of story in the first expansion, easy math suggest that the second one will be twice as long, and hopefully worth waiting for.
And yes, there will be new Gwent cards in the expansions as well.
Source: DualShockers.