CKEditor: *During* WYSIWYG edit, how to show caption beneath image? When editing a body field with image and caption, the caption does not display during editing. Once saved it is visible - when the content is viewed.

Implementation-wise, I've added a caption field to the Image entity via the Entity View Mode config pages - admin/structure/file-types/manage/image/fields

Any thoughts on how to get the caption to show during edit?

CKEditor 4.3 supports captions but there would need to be support for the Drupal side of the implementation.
As of CKEditor 4.3, they now have widgets in the CKEditor side. They have introduced the Image2 plugin/widget, which supports image captions. The problem I've seen here is that Drupal has not caught up with this, so if you're using the media module for a file browser, it looks like that functionality is not yet ported to this newer version. However, if you just care about captions, it works. 

See: http://ckeditor.com/addon/image2 for the plugin. I've been using it with the CKEditor Module, but it should work just as fine with WYSIWYG + Ckeditor Library.