My buds over at ReelzChannel emailed me to let me know that although 30 Days of Night hasn't even opened yet (it comes out in a few days) there's already talk of a sequel. Here's a brief quote from an interview they'll be releasing tomorrow with screenwriter Brian Nelson regarding the possibility of a sequel happening:
"I'll just tantalizingly say it is possible you might see more of The Stranger [a main character in the film] in the future."
Look for the full interview tomorrow on their site.
Source: ReelzChannel (Be warned, there are plot spoilers on that page)