To my knowledge, Larian have never made an expansion for their games. I expect BG3 to get the same treatment as DOS2: a definitive edition in a year or so, during which time other parts of the company begin development on one or more new games.
Larian has never had such a massive IP in their stewardship before, either. The size and success of BG3 dwarfs every other game they've made, so a DLC is a lot more likely under these circumstances. The financial incentive for a DoS II DLC may not have made sense, whereas it's probably a foregone conclusion that BG3 is getting more content. I'm sure Wizards of the Coast will have a say in the matter as well, since every other BG game has had DLC. I'm optimistic.
I think if it were a foregone conclusion we would have heard something by now. And I doubt that the fact that the other BGs had expansion packs matters that much, because those prequels were so far in the past and done by an entirely different studio.
I actually don't have a lot of hope for an expansion pack; I think they're going to be combating bugs and issues in the current release for a long time.
We're not going to hear an xpac announcement 2 months after release, regardless of whether or not it's already in the works. I agree that they're going to be squashing bugs for a while, but eventually, a boardroom full of Wizards execs are going to start pointing at sales figures and factoring in precedents (BG 1 & 2), and - assuming it's not already written into the contract - they are going to lobby for more BG3 content. It's purely a financial decision, now that Larian are in bed with Wizards of the Coast. This is why BG's legacy xpacs matter, and it's also why the fact that the story of BG3 is "self contained" really doesn't matter. Larian may technically be able to say no and move on, but if they'd be leaving millions on the table, there's no way they'd do it, it'd be irresponsible to their employees and to the success of their company. I think BG3 is such a massive phenomenon that that's the situation we are in.
