According to the Mat Men Pro Wrestling podcast, Brock Lesnar is not booked for Summerslam due to unspecified creative differences. WWE still wants Lesnar to appear, but also wants him to have him appear on live events. There is no word on when Lesnar will return. His most recent appearance took place at WrestleMania 36 and his contract has since expired.
Lesnar being back could mean a lot. Check out some of his conquerings: