It's not uncommon for people to flesh out answers incrementally for the sake of posting first. Usually this gets the key point out and then more detail is provided shortly afterward.
It would be nice if there was a checkbox in Answer/edit mode that could be set by the user to indicate it's being worked on, or more is coming. This would be reflected to viewers by the current answer and a note "This answer is in progress...".
The progress status would time out automatically if two minutes pass after the last edit was made to the answer.
Edit: This addition could solve problems including but not limited to: premature voting by assumption of a final edit when more are pending, allowing questioner to get answers early and iteratively, users to have less "exam" stress trying to blurt things out quickly. Overall it can contribute to a healthier answer base.