On September 1st, you will no longer see advertisements utilizing Flash. This doesn't mean that you won't see video-like advertisements anymore, just they will all be HTML5.
Google's AdWords division states that this change will speed up browser performance and bring all advertisers in line with the new HTML5 standard.
There is already a setting in Chrome that allows you to disable these Flash advertisement plugins, but on September 1st, Google will switch this to “On” as default in the Chrome browser.
If you're an advertiser, Google has already attempted to convert your Flash advertisement to HTML5, but there is a chance that it was unsuccessful in doing this. If it was unsuccessful, then your advertisement will be disabled and you will need to do the converting yourself.
Google had the following to say about the changes:
Video and interactive media bring consumers rich, engaging experiences on the web–but they can also impact browser speed and battery life. A few months ago, Chrome introduced a setting (https://goo.gl/cBhea4) designed to increase page-load speed and reduce power consumption by pausing certain plugin content, including many Flash ads. As soon as September (https://goo.gl/u5f019), this setting will be turned on by default so Chrome users can enjoy faster performance and view more content before charging their batteries.
Source: Google
