Could DC Extended Universe be introducing Supergirl?

A rumor circulating the internet this weekend says that the DC Extended Universe (DCEU) could be introducing Supergirl in their untitled Superman sequel which currently does not have a release date. The rumor was first posted anonymously on 4chan.org this past Monday.  Whether there is any truth or not remains to be determined.  It’s likely all speculation but with the success of Wonder Woman, DC is probably looking at all of their books to get…

"Could DC Extended Universe be introducing Supergirl?"