I have read that CD Projekt, after listening to player suggestions, will improve the interactions with Triss and probably other characters, fixing the imbalance many have felt. It's very rare and commendable to see a team so willing to listen to criticism and act on it, especially when the criticism hasn't been shouted (as was the case with MASS EFFECT 3). So in that spirit, I'd like to propose a post-credits game state. It would require enough work, I reckon, to be a minor expansion. I, for one, would happily pay for it.
Right now, the game reverts to a pre-last-chapter state after the credits roll. The final outcomes of your many choices are explained in narration, but not reflected in actual game content. As a result, the game doesn't feel nearly as alive as it does when the main quest is still there. Problem is, it's tricky to explore the entire world while the main quest is active, because there's an implied urgency to it. This is a common problem with open-world games, one that stops being a problem if the main quest ends and segues into an adequate endgame.
Take my playthrough, for example:
------- (Triss and Geralt spoilers ahead). -------
Geralt ended up in Kovir with Triss. I have learned this through narration. Now imagine this being in the actual post-credits game: a very small representation of Kovir marked in the world map, just their house, non-explorable. You see it only through cutscenes. When you first get there, you get a cutscene that establishes how life is going to be when Geralt is there, a nice moment between him and Triss, enjoying what they have earned for themselves, and after an indefinite amount of time passes, Geralt goes back to the main game areas to do some Witcher's work. And from then on, every time the player goes back to the house, one of several possible cutscenes play between Triss and Geralt representing various aspects of their love life, an indefinite amount of time is implied to pass and finally we see Geralt leaving the house to travel back to the playable areas. It's purely for immersion. Knowing that there is a house and a loved one you can go back to. A comfort you have earned.
Besides that, there could be some post-credits quests to wrap up Geralt's relationships with many characters. Something that establishes, without needing narration, where things stand with everyone. The player would be free to get to those quests whenever they like, exploring other things first if they so wish. Something to look forward to when all the side quests have been completed.
In short, content that allows the game to transition to a post-main-quest state rather than a pre-last-chapter state. [EDIT: This would also be more expansion-friendly, by the way]. One where it feels like Geralt is living with the choices he made rather than these choices never seeming to have taken place. That way, the player can finish the remaining side quests and Witcher contracts and explore the world while feeling like it has evolved. Like it's a whole. Right now, the pre-last-chapter state feels tacked-on rather than organic. Narration over concept art will never feel as real and lived as events taking place in the game itself.
All that being said: THE WITCHER 3 is my favourite game of all time. Without a doubt. And mind you, I didn't have a favourite game of all time before. Many games competed for that position in my head. THE WITCHER 3 rose above them all. It's that special, as are the people who made it. A magnificent work. Thank you, so much, for the privilege of playing it.