If you've played The Witcher 3, you're familiar with the card game Gwent. You probably enjoy that card game a lot. You may even be hopelessly addicted to it, to the point where you spend more time playing Gwent than actually witching.
If that's the case, there's good news for you. CD Projekt Red has filed a trademark for something called Gwent: The Witcher Card Game. And they've filed it in the category of "videogames, software etc", so it's obvious that we're looking at some sort of digital release, not a physical card game. The filing even has a logo!
CD Projekt Red have said that they're showing new games at E3, and that those games aren't Cyberpunk 2077. So the obvious conclusion is that we'll see a Gwent reveal next week.
Nerdleaks has a few more details.