On the Adwords Google+ page, Google just announced a timeline for banishing Flash from its advertising network, announcing that "Google Display Network and DoubleClick Digital Marketing are now going 100% HTML5."
Starting on June 30, 2016, Google will no longer accept new Flash display ads from advertisers. On January 2, 2017, even old Flash ads will be blocked from appearing, making Google's ad network mostly Flash-free. The one exception seems to be video ads, as Google notes that "video ads built in Flash will not be impacted at this time."
Google has been trying to wean advertisers off of Flash for some time, providing tools and best practices for switching. Now it apparently feels good enough about the switch to force it on everyone.
Even Adobe seems like it's finished with Flash. It killed Flash Professional—its Flash authoring tool—in December, and today announced Adobe Animate, which outputs projects in HTML5.