So what do you think happens after the credits roll (Spoiler)
The mother's exposition says something about how she had to kill those families so that Agent Harker could live. But at the end, Agent Harker saves the little girl. She kills both her mother and Blair Underwood. So does that mean the devil is going to get Agent Harker?
At the end, she tries to shoot the doll's head off. But it's unclear if she ran out of bullet or if her gun is supernaturally misfiring.
Another detail is that the little girl still seems comatose. She just saw her father shot down, and she saw Agent Harker shoot her mother. Yet the little girl continued to sit there leaning her forehead against the doll. My guess is that the little girl is already gone, basically. She's probably going to end up like Carrie-Ann in a mental institution.
But what happens to Harker is left unclear . I don't think she lives or ends happily. Right before she shoots her mother, her mom screams at her, "Stop calling me that (i.e. mom)!" So I suppose the mother was possessed by either Longlegs or Satan. I think Longlegs or Satan will end up possessing Agent Harker and possibly use her to bring more murders, the way Harker's mother did
Anyways - great movie. Lots to think about