Any newsletters within the scope of MediaWiki.org can be created. In
previous discussions it was agreed to only allow administrators to create
newsletters. Once a newsletter is created, their publishers can announce
new issues at will without requiring administrators anymore.
PS: BIG THANK YOU to everybody involved in this project. Proper attribution
and celebration will come in a blog post summarizing these ~2,5 years of
planning, development, testing, and deployment to a first Wikimedia wiki.