Depending on what game(s) they have in the pipeline to start once BG3 is 'done', if they see a big enough push for modules they might be financially swayed to do an official one. What I mean is that if they see a massive surge in modding and huge population of people playing those mods, and IF they judge that it would be financially worth it for them to spare the resources to create a module, like Storm King's Thunder, then I could see them doing it. It shouldn't take them anywhere near as long to make as the base game because they wouldn't need to create any new systems, though they would have to create new models for creatures/monsters they haven't built yet, the whole world for the mod, voice acting, so it still wouldn't be 'quick' but shouldn't take as long as the base game took.
I hope you are right. I think once the game is released, one of the priorities apart from bug fixing ought to be making the modding/scenario creation in Baldur's Gate III so enjoyable and easy that there is a huge amount of new content created. D&D players are highly imaginative. It Larian provide the infrastructure and tools for Dungeon Masters to jump into, the game will take on a life of its own.
I hope Larian look at the game from the potential DM's perspective. What friction could be removed that would get modules into motion? For example, mods benefit from each other if they are interoperable. Larian could maintain and official matrix of module compatibility. (Modules A, B, C, D. A is compatible with B and C but not D. B is compatible with A, C and D, etc.) To have a place on this matrix, it would have had to have passed some sort of Larian ocverseen quality control. There might be some goodies for people who produced widely used mods, etc.
