Yes, there will be an Insidious sequel
For those who reacted to the last few minutes of Insidious—last year's astral-projection horror thriller "from the makers of Saw and Paranormal Activity"—by leaning towards the screen and yelling, "And then what happened? Then what happened!?", there is good news. Director James Wan, writer Leigh Whannell, and Jason Blum are reuniting for a sequel due in 2013. In making the announcement, Whannell said that both he and Wan "feel that we can mine more terror from the world we created, and know that if we assemble every member of the original team, we will have an amazing continuation of the story for fans of the first film."
In the meantime, Wan is hard at work on another horror flick starring Insidious' Patrick Wilson, as well as Vera Farmiga, Ron Livingston, and Lili Taylor. Tentatively titled The Conjuring, it's the "true" story of a haunting at a New England farmhouse—though presumably it's "true" in the contemporary sense of the word, meaning that it didn't happen but it says it did on the poster. It's not yet clear whether Wilson or co-star Rose Byrne will also be part of the "original team" that will be reassembled for the Insidious sequel—especially given that Byrne’s star has risen a bit since then thanks to Bridesmaids. But if Wilson’s character does come back—no spoilers if you haven't seen Insidious, really—but we’re just saying, maybe don't trust that guy.