Quite unfortunately, that ship has totally sailed as it isn’t just a matter of larian not wanting to make a dlc. They physically cannot do so at this point, as with their announcement of no dlc/sequels they explained that the IP has gone fully back into the hands of Wizards of the Coast. Larian owns the game itself and the engine it runs on, so they can continue to make tweaks and alterations to the content of the game, but any significant changes to the game’s plot at this point would directly violate them no longer having the IP. This is also why there will never be a level editor/quest builder officially supported for this game. Larian obviously knows that’s something that would make the game explode even further in popularity, but they’ve said it’s not going to happen. Theres no confirmation as to why, but the reason is absolutely because making a level editor in this game would directly invalidate the Digital Tabletop that WotC is creating, and they obviously prohibited Larian from making a level editor so they can maximize their profits from their upcoming product.
All we can really do is speculate as to why Larian decided they didn’t want to continue with licensing the IP. Their official statement is that the entire crew is burnt out from BG3 and wants to put their passion towards a new, original project. This is definitely partly true, but I don’t buy it fully because of how sudden the announcement came and how abruptly they said there would be no substantial new content after several months of post-launch support addressing major points of player feedback. Something definitely caused a dispute over the IP, and Larian decided to cut their losses and leave the game behind. I wish we could have gotten more, but it seems like all we’re getting now is mechanical changes, meaning the plot will likely forever remain kind of a mess in the third act. The only hope now is to make such a loud pushback as a community that they reconsider their decision and talk with WotC again.
