From the topic Some questions to devs:

Originally Posted By: Lar_q
- Will the world be open and bigger than DD one?

It's pretty big, but it's very hard to compare directly. Measuring the size of the world is not just a questions of measuring the relative size, you also need to take into account how much you can do in that world and what parts are accessible, what not. I actually don't know how large the div world was.

As far as length goes, a couple years ago the tentative plan at the time was to create a 20 hour RPG, with the possibility of adding 10 hour chunks (FWIW, D2:ED started off as a 25 hour RPG); see the old topic Next title Larian works on?. Official DLC hasn't been mentioned since, so it wouldn't be surprising if the current design is a single, longer game (not counting the user made DLC with the included editor).

I don't recall seeing more recent comments on the game size or length (other than a blog post saying the E3 presentations for Dragon Commander and Original Sin were refined to " 40 hrs of gameplay in 15 minutes..").

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