By using google for example. GDC was already this year and the next one is at the end of march 2024, plus it's game devs for game devs, which means you don't advertise things here, unless I don't know, maybe they'll want to hire some freelancers while they move onto thw new project
Regarding the timeline, any possible definitive edition will come out in August next year at the earliest, but more likely in late 2024 / early 2025.
As for the event itself, they discuss their work process and I'm sure people there will be asking them about their handling of different aspects of the game. Swen himself thinks Act 3 will be the main topic. Patch 2 will likely be brought up in terms of how fast it came out and how Larian managed to do it on such short notice.
That being said, nobody here expects updates about the game there. So I again don't know how you came to the conclusion that they won't be working on the game anytime soon or at all just because they're attending the conference.
