There's a fairly long interview with several members of the Dark Messiah development team at CVG. Alastair Halsby, Romuald Capron and Julien Roby answer all kinds of questions about the game. Here is what Capron had to say about a possible sequel:

"When you play [Dark Messiah], you'll see there's a great story, just that. At the end, I can tell you you'll want to continue. I won't say more on that part. I think something quite unique has been started with this game... there's so many things that you can always do better. We already have very good physics and interesting work with the environment - this is something we can certainly grow, there's so much stuff we can do beyond that. You know, stuff people like to see is even more enemies on screen, even bigger battles - even though there're pretty big battles in the game, you can always go beyond that.

The official forum has become a jungle since the release of the demo. You can find solutions to various technical problems, tricks to enable hidden features and more.