RPGs always have some levels cut in development and I wouldn't expect Larian to finish the megadungeon bits unless they were somehow integral to its overall story. I'm not sure why Swen thought it worth mentioning tbh as I'm assuming there is plenty of megadungeon as is, though the cut bits would be cool to give to the community as a modding/learning opportunity if nothing else.
I guess he mentioned this because during Kickstarter 11 dungeon levels were reached - and I think some people would start counting the level dungeons during the game and complain that less than 11 levels are there
