According to our friends at Latino-Review, Marvel has hired two new writers to rewrite the script most recently revised by Adam McKay. Those two screenwriters are Gabriel Ferrari and Andrew Barrer. They are production writers, which means that they will be on the set of the film while it's shooting in Atlanta. So they will constantly be working on the script and making revisions during production.
This really isn't a big issue as it is a common practice in the movie business. There's a good chance that these two guys won't even get any screen credit. That will be up to the Writer's Guild arbitration committee.
Ferrari and Barrer broke into the business out of NYU with a 2010 Black List script they wrote called Die In A Gunfight. They also worked on a draft of a big screen adaptation of Sabrina The Teenage Witch for Sony. According to the site, it was that Sabrina script that impressed Marvel, and they went on to offer them the Ant-Man writing gig.