I really hope there are more DLC or, preferably, expansions to come out after the two announced ones. I imagine the two that will come out will greatly add to the story, and adding a new area will always be fun, but in the end I'd really like a DLC that would make the end game more complete. As I felt that after the way the whole story progressed, the end game and epilogue, just felt very vague to me, and kind of left me lost and in the dark as to the futures of the characters. I mean no offense to CDPR when I write this, as I probably feel that way because the rest of the story was so great. But the end felt a little cut off to me, and I felt the story deserved a little more explanation and content to put a better close to it. Throughout the story, talking to Triss/Yen(whoever you chose, if you did choose) about their plans for after their mission was over, the rest of the Witchers from Kaer Morhen (Keira[if she is around]/Lambert), and the others (Zoltan, Dandelion) and obviously, Ciri. A DLC/expansion just putting more emphasis on to their lives after the White Frost, or at least including them in the world after the game is done.
When I frst finished the game, I felt lost and disheartened at the empty world devoid of any of the main characters. Even if it's not a full DLC, just little additions for continuing contact with the characters, Zoltan/Dandelion at the Chameleon, Triss at a house in Kovir, Yen at a house where she chose, and CIri out on her path, whichever she ended up on. Even if they are not full blown storyline additions, something to remain in touch with those you've shared the adventure with. Alsdo I would not complain if they did add more romance with whoever you chose in game, not asking necessarily for more full blown sex scenes (although would like that), just more time with the one you chose to add a little more depth to their relationship.
This would be my greatest hope for any future DLC or Expansion to the game, if it will happen only time will tell but, I would GLADLY pay extra for something that added this to the end of their story.