Yeah. However we got here, Karlach is a great character that gets shafted by the story.
I could handle Wyll being doomed beyond any possibility to save- "You literally sold your soul to a devil, ya dingus" makes much, much more sense as an unavoidable doom to me. There's some logic for why solving that problem might just not be possible. (not suggesting they change the game to make him screwed to be clear, just saying it would make more sense for someone who voluntarily sold their soul to be unavoidably doomed than "No, you can't have any of the skilled artificers that owe you their lives fix this infernal artifact, or replace it, or use powerful healing magic, or call on one of your half-dozen extremely powerful allies for help, or try to deal with the devil that's been trying to cut deals with you for three acts now, or....)
I don't want to get my hopes up too much without more idea what is/isn't planned- if there's going to be a DE, for example, there's been no official word, even though they'd already have to be working on it. But I would hope for, at a minimum, some expansion of the Avernus ending, since if it was meant to be hopeful or positive, it totally missed the mark there for me- and from the sound of it, a lot of other people. What I'd *like* to see is a full DE that makes some substantial revisions to act 3 and especially the ending, because Karlach's ending is far from the only part of the ending that's really weak, just the part that stings me the most. (there's a reason a lot of people are unhappy with how Astarion's story can end, as one example)