They've said they're going to focus mainly on bug fixes and quality of life improvements going forward. And they seem to be treating the release of mod support as an unofficial hand off of the game to the community. Even though they won't be releasing anything that provides the modding community with true creative freedom. From what I can tell it's primarily meant to be a more streamlined way to make cosmetic changes, cheats, and spell additions/adjustments. And a way for console users to access mods.

Larian does listen to player feedback which is why I'm hoping they'll be open to changing their minds about a definitive edition at some point. But as of now I don't think they intend to truly build upon the game in any way, at any time. They can revisit their partnership with wotc but until/unless they do I imagine what they're able to do with the game is very limited. For example they can hardly add companion reactivity in act 3 when they no longer own the rights to the companion characters.