This is a question that I often wonder about. We are all familiar with the incident of Jesus sending Legion into the herd of pigs because the demons didn't want Jesus to send them into the abyss (Luke 8:31). However once Legion went into the pigs the pigs all went over the cliffs and drowned. So my question is where did the demons go after their new hosts all died? Wouldn't they have gone into the Abyss anyways at that point? I'm just curious as to what the 'theology' says about it.
Since God didn't tell us, it wouldn't be appropriate to speculate. I wouldn't even know how to begin to arrive at a conclusion that involved the spiritual realm when we are given no information.
Thanks for your answer. It was actually a confirmation for me. I had come up with the same conclusion every time I thought about it.