WolfheartFPS mentioned 2000 and (I think) that half were interactable, even if it was only a simple phrase. I'm not sure where this was coming from, perhaps from something that was said at Ghent?
Unfortunately my notes on Ghent, like Wolfheart's, weren't clear. Swen definitely mentioned in the presentation in the morning that we both attended that there were around 2,000 NPCs, but neither Wolfheart nor I managed to note whether that was just in the city or the game as a whole.
Separate from that, Swen said that more than half (I think he actually said 50-60%) of the NPCs in Baldur's Gate city were interactable with, with the rest being crowd figures to make the place feel more lived in. A lot of those interactable characters might only have one line, but Swen told us that some of those lines could change depending on what we'd done in the game so presumably they could be different on different playthroughs or on when we talk to someone. Plus I saw there were lots of people just chatting about stuff we could eavesdrop on. And then plenty of characters who have more to say and quests to give.
So, safe to say, there are a lot of people to talk to both in the city and the game as a whole.
Yes, I don't think it will feel empty either way. I'm even wondering if that won't be somewhat overwhelming.
I always hope to find an option to disable the "!" quest markers on NPCs and on the map, so I can play it old school (with the help of the journal), but I suppose it's not realistic to design such a big game like that anymore. With 2000, 1000, or even 500 NPCs, even if only half of them are potentially involved in quests, the game would have to be sold with a thick notepad, a pack of pens, and blister bandages. Even with the markers, it will be a lot to take in.
Even with the markers, it will be a lot to take in.