As you already know, Google is removing the ability for advertisers to use Flash format for their ads in the Google Display Network and DoubleClick Digital Marketing. Well, starting tomorrow, you will no longer be able to upload ads in Flash format.
Google said they will only accept the HTML5 format for animated ads.
Google reminded us of this on Google+ saying:
In February, we announced ( https://goo.gl/XXkpyE ) that the Google Display Network and DoubleClick Digital Marketing are now going 100% HTML5. Starting June 30th, 2016, display ads built in Flash can no longer be uploaded into AdWords and DoubleClick Digital Marketing.
AdWords advertisers who use Flash ads in their campaigns have several ways to ensure your creative can continue to show on the Google Display Network. Read more here: https://goo.gl/ZBq5DR
So hopefully this won't be a surprise for people tomorrow.
Forum discussion at Google+.