Via Barry Schwartz | @rustybrick
Google announced on the Webmaster blog that they are going to be boosting the effects of themobile-friendly algorithm they launched back on April 21, 2015.
The mobile-friendly algorithm is a page-by-page signal, so it can take time for Google to assess each page, and that may be why it will be a gradual rollout. And depending on how fast Google crawls and indexes all of the pages on your site, the impact can be slow to show up.
It is believed that this rollout will have less impact than the original mobile-friendly update, which was called "Mobilegeddon." The original Mobilegeddon was supposed to have a significant impact on the mobile results, but not everyone said it had that much of an impact.