I'm surprised to see this actually happening, I know people were asking for a standalone version of Gwent but for whatever reason I never expected to see it. As single player side content it was a fun distraction but I would have to imagine the game will need a good deal of tweaking to be a satisfying multiplayer experience (ie not just play as many Spies as you possibly can and tap your opponent out). It's being said that though it will primarily be a multiplayer card game there will be a full singleplayer campaign as well.
The game's coming out for Xbone, PS4 and PC. If you want to sign up for the beta in September go to playgwent.com and try not to scream at Triss' terrifying face.