The Witcher 1 & 2 were both focused heavily on story. They wanted to suck the player in by telling a deep story and also have the player make tough choices where the consequences were oft times unforeseen. There was no clear "good" or "bad" choice and many times you wouldn't see the consequences of your actions until much later in the game.
One of the biggest changes to how The Witcher 3 will play is that it will be open world and not location restricted by chapter like the previous two were. They've supposedly revamped the entire combat system as well.
What I found with the combat system (in Witcher 2 anyways) is that it was a solid mix of combat in the ways you see it in Batman: Arkham Asylum, Assassin's Creed and Fable (Of course not
taken from, looking at release dates and all that.). Every movement felt smooth and appropriate, and the fights felt dynamic and unique.
Open World, however, can mean a lot of things. Fable did open world, but not in a way I would like to see it in The Witcher. You were free to explore any part of the map at any time, given some restrictions, but there was literally
nothing to do if the main questline didn't take place in that location. I felt the jobs were quite bland and boring, and a complete waste of your time to be honest. I would like for, in all of the locations shown in this trailer and more, a variety of activities, either with a corresponding story, or at least compelling enough from a gameplay-perspective that you will be able to tell one experience from another in retrospect.
Weekly tournaments that you can participate or watch, place bets on and hear about from wanderers when travelling the countryside. This would force your mind to make an imaginary calendar, with dates for what then feel like appointments written on it. You could take part in, after completing an introductory quest for them, a hunting party, organised by a hunting club in a town. They would host one of these every 20 days, and you would be able to look up when they are and then decide for yourself:
"Do I wish to attend? After last week's tournament in City A, which I unfortunately missed, I might want to participate in the tournament in City B to catch up on points in the Tournament Season Leaderboards. If I miss more tournaments, I won't have enough points to participate in the Silver Fang Tournament at the end of this month, and have to settle for the Ironbark Tournament instead, whose prizes are nothing compared to the previous.
However, if I do well at the hunting party, I will be one step closer to being appointed Guild Master, allowing me to choose dates for parties myself. This would yield some good income for me, and would be a nice pastime."
I want to be able to feel the weight of certain decisions, yes. But those decisions don't necessarily have to impact the story in any way. They can be as minor as choosing one party over another, which will increase your relationship with one faction and sour the one with the other.