According to Blizzard, Diablo 4's Patch 1.1.3 will be released on August 29 at 10 a.m. PDT.
The patch will fix multiple quest bugs and introduce several quality-of-life changes like monster crowd control adjustments. After the initial patch notes release, Community Manager SinfulScribe has clarified in a Reddit thread that the update will be released next Tuesday morning:
Diablo 4 Patch 1.1.3 Patch Notes Diablo 4 Gamescom Interview
Earlier this week, Blizzard revealed Diablo 4's second season during Gamescom Opening Night, Season of Blood, which will release on October 17.