Flash continues to exist largely because it's so entrenched. Even as mobile devices without Flash become increasingly common, you might notice ads are often still created in Flash. Google is looking to change that on its ad network by automatically converting Flash to HTML5. That should take some strain off your system.
Google started offering advertisers the option of backing up Flash ads as HTML5 last year. These ads would then be served on devices where Flash was not supported. Now Google will start doing that automatically for all new and existing Flash ads that are served on its Google Display Network and the DoubleClick Network.
Advertisers won't get a lot of feedback on when their ads will be converted to HTML5 at first, but Google is working on a system that will show the status of Flash conversions. This is important because not all ads will work as HTML5, so you will still see Flash for the time being, even on Google's network. Maybe one day it'll all be HTML5, but at least we're a little closer now.