Thread necromancy?
Well, I'll toss in my two cents, all the same.
Weekes did say he'd like to (if possible; he may be overruled) conclude the Solas romance arc in the next game, assuming there is a next game. We don't know for sure yet that there will--it seems likely but has not officially been announced, and no one's allowed to admit if it will come to be or not.
If there is a next game, we will not be able to play the Inquisitor (at least, not from what the developers have said about the Inquisitor's story being done with), so even should the romance arc be concluded (whether "happy" or "sad" or not), we'll be less connected to that conclusion. We'll only be seeing it second- or third-hand, maybe not even on screen but more as a codex entry/letter/etc. through whatever character we're playing at that point.
Ideally, I'd prefer if we had a dual protagonist game, where maybe the Inquisitor, even if he/she isn't adventuring any longer, is used in handling some aspects of the game, and the new protagonist is the one who goes out adventuring. Then, we could follow the Inquisitor in a nice little cutscene, and control him/her in that confrontation with Solas.
Those of us who romanced Solas are not the only ones invested in seeing the outcome between Solas and the Inquisitor. Whether you loved him, hated him, or were friends with him in your playthrough(s), the connection between the Inquisitor and Solas is personal in a way that it cannot be between Solas and a new protagonist. As such, it would be most meaningful if the player were able to handle that interaction how they choose to, and that means a nice cut scene. But realistically, the developers are going to want to spend their resources primarily on our new protagonist, and that makes it less likely we'll get a moving cutscene and more likely we'll see it wrapped up in text via codex, a letter, or even an ending slide if Solas is truly the Big Bad of DA4.
And that's still assuming that there's a DA4. If there isn't, we're left lingering in headcanon territory--which can be both better and worse than what might exist in an actual game.
All we can do for now is trust that Patrick Weekes will find a way to conclude that arc in a way that leaves us satisfied, even if it isn't necessarily happy. Honestly, not sure if it can be happy because it'd be difficult to trust Solas after learning he ended the world once and was willing to end it again, even if it meant hurting you tremendously--even telling you was obviously painful to the Inquisitor (okay, most Inquisitors--some might be a bit evil or something).
In the meantime, you could always vent your post-Trespasser DLC frustrations via writing a post-Trespasser Inquisitor/Solas fanfic, or go read others' post-Trespasser fics. (No, this is not a plug for my fic; it's not post-Trespasser and would not offer anything in that direction). I'd argue that while some such fics are definitely out of the line of canon etc., others are really well done and feel like they could certainly be a part of the actual story.