They were also exhausted at that point. I suspect the first profit-sharing check has changed everyone's minds.They initially basically said that, which is why this is news.
Swen specifically downplayed any idea that they might do DLC or a sequel and when talking to journalists at the final Panel From Hell and initially just after release. He went on to suggest that:
A) Larian probably wouldn't work on an AAA game this large again any time soon, maybe ever (this is similar to how Bioware acted after completing the ME series "Whoa that was hard, let's not do that again!").
B) Larian would probably instead work on a number of smaller, more contained games, which, from the way he said it, made it sound more likely they intended to go back to not-really-AAA or even definitely-AA games.