Specifically, it means that more information is required to complete the task (e.g. requesting the filename for saving a file). If the action is literally about opening that dialog (e.g. something like "Show Properties"), the ellipsis is not needed.
The practical use is that the user knows they will still have the opportunity to back out of the operation, and not commit to it by the first click. I don’t think “will need more input” is that useful as an information by itself.
The practical use is that the user knows they will still have the opportunity to back out of the operation, and not commit to it by the first click. I don’t think “will need more input” is that useful as an information by itself.