At least insofar as monster movies go. The Descent, which I think is a phenomenal film, didn't really need a sequel, but neither did Alien. I adore Aliens - I'd probably rank it in my 25 favorite movies of all time - and so maybe The Descent Part II will live up to its spiritual predecessor's achievement. There's a trailer out that gives me hope.
Frankly, I didn't even know Marshall was done making it, let alone that it'd be coming out in December (in the UK).