I'd definitely be excited to see more things added, especially within act 3 to improve story cohesion, companion depth and reactivity, as well as fixing inconsistencies and bugs that are currently still in the game. However, we'll have to look towards the modding community when it comes to any of these ideas, I'm afraid. Larian has clearly stated in their patch 8 announcement that aside from minor bug fixing, they will not be bringing out more patches, expansions or anything else. You can find the announcement
here. They have moved on to their next projects as they have two separate teams both working on new RPGs that are not related to Baldur's Gate.
Honestly though, it seems that even for bug fixing, you'll have to look at the modding community at this point. My personal experience is that bug reports also no longer get addressed at this point unfortunately. A bug introduced in Patch 8's stress test in January (Lyrthindor's bugged combat encounter in Shar's temple) has loads of topics on it on Reddit including videos of the bug in action for example, but as of right now that bug is still in the game and I personally haven't found a response from Larian acknowledging that they're aware of this and planning on a hotfix for it. So Larian has taken their hands off of BG3, left us with a (mostly) outstanding game and the rest is up to us to either fix in the case of bugs, or create/add in the case of enhancing immersion, weapons, spells and/or DLC-like content.
Especially for existing characters it will be a nigh on impossible task to add anything, though. With a game that is fully voiced throughout by either the characters speaking or the narrator going through a character's inner thought process, you'd need their voice actors to consent and collaborate with any form of addition you'd like to see. You would also likely need the consent of the original writer of a character to add anything new to their established character. So it's probably more likely that we'll see (smaller) custom campaigns as passion projects in the future, with entirely new and original characters, potentially with new voice actors recording their own lines, to create a new and lively experience.
