This is what i hope too: Think about Baldur's Gate 2: The city was really big, on relatively small room. It had hidden rooms, some stairs, a sever and so on on relatively small room. This could be done in Pillars too: On one day there is a market in the city where a lot of things get selled: from food to weapons to various other interresting things (think that you buy a pendant and then a questline starts); on the other day (at night) you get attacked by thieves. Same room, completely different story.
Also shouldn't Pillars of Eternity be moddable like they said it on the News (because this is one of my personal points that i pledged to it)? If yes, it should be possible to add unlimited of content; simply think of Skyrim: there are so Mods that are even better than the game itself: This does not mean that Obsidian will not do a good job (for example: the story of Fallout: NV was better than FO3), but there are always excellent modders. So i really hope that it will be so.