Imo, the character who has the most potential to die in this DLC is the Inquisitor themselves...I don't know why I feel that way...
I wonder if we'll actually get some closure on Hawke/The Warden in this DLC since it's pretty heavily hinted that the next game is going north. I don't know why Bioware won't want to wrap up the previous heroes' storyline since this DLC seems to be the finalest final adventure for the Inquisitor.
Since we'll be able to chat up both Varric and Leliana there's a chance there will be a dialogue option (provided Warden and Hawke are alive ofc) along the lines : Hey, is Hawke back from Weisshaupt yet/how's life in Kirkwall, did the Warden succeed in their quest/are they on business in Ferelden?, etc.
One interesting thing I realized is that Leliana is the only romanceable companion from Origins who is friends with the Warden and is still in contact with them, while Alistair sort of speaks about the Warden with disdain especially if they did the DR and Morrigan only says how grateful she is to the Warden but only if they allowed her to do her Ritual.
As if Inquisition din't already clearly point it out, Varric/Leliana are the only characters left that connect us with the previous heroes.
I didn't see the trailer (I want to keep the surprise) but I do feel the same way... Just yesterday as I heard Xenon telling my inquisitor if he could keep his hand when he dies when I entered the Black Emporium, I thought that BW could not let such a powefull playable character live, so I'm guessing that either he would die or get his anchor removed
I also hope that we'll get a closure for all past stories including the Warden or Hawke or at least a clear glimpse of what will happen to them (something more than just the vague "he's somewhere, doing something, he's busy, you can leave a message" that could fit everything of course). I don't care how it is told or what it's told as long as it make sense and take previous choices into account. (for instance, I really enjoyed the letter from Leliana in Awakening, even if it was almost nothing...we knew what she was doing and we could feel that the relationship was still going on and it was enough for me)
As for Leliana (I understand that she will have some importance in the new DLC), I really hope that we'll get more details about her and the Warden, what we had in Inquisition was, well... very light. She totally forgets about her lover when thinking about becoming a Devine, she couldn't find the Warden when looking for him/her with Cassandra... It would be good to have something more elaborate too.
*sigh* 'Looks like a lot of non-main-story related things for such a DLC... I can dream.