AdWords Moving to HTML Only by 2017

Google AdWords announced that they are transitioning to HTML5 ads only by January 2, 2017. Their reasoning for this is

So you can reach the widest possible audience across screens. To enhance the browsing experience for more people on more devices, the Google Display Network and DoubleClick Digital Marketing are now going 100% HTML5.

June 30, 2016 will be the date that Flash ads are no longer accepted and on January 2, 2017, Flash ads will no longer be displayed. To learn more about changing flash ads to HTML5, visit the AdWords Support pages.