Riot Games released a preview for Patch 12.15. The upcoming update features buffs to energy champions along with Thresh, Leona, Lillia, and other characters. Master Yi, Qiyana, and Gwen will be nerfed. This information was shared by the games balance designer Matt Leung-Harrison on Twitter.
Zed, Lee Sin, Akali, Kennen, and Shen are the mentioned energy champions who were buffed. The main reason is that these characters couldn't keep up their energy costs after the durability update.
With the 12.15 update Riot will also nerf Divine Sunderer and First Strike, while buffing Mercurial Scimitar and Silvermere Dawn.
The changes will be detailed in the following days and will be available on PBE-server. Patch 12.15 should be out on August 10.