No editor should be added to the core of Magento. Only via plugin, cause everyone has their own choice of what they use. Some like tinymce others like fckeditor etc.
No need to talk about which is better, have a neutral stance and create a sample editor plugin that can be used as a guideline for plugin editors.
If wysiwyg editor will be made it will be definitely a plugin… I have yet to find one that plays nice with templated code, like dynamic URLs in <img src="{{url}}"> or <a href="{{url}}">
