As of now, the SummerSlam main event is still expected to be Roman Reigns vs. Brock Lesnar for the Universal Championship, according to Dave Meltzer on Wrestling Observer Radio.
Braun Strowman did defeat Reigns last night, which would make it seem like Strowman should be more deserving of a title shot, so we’ll see how WWE handles things. Obviously, their plans could also change.
Reigns did also attempt to murder Strowman, so it would seem weird for their feud to just suddenly stop now and for Reigns to just move on to Lesnar and for Strowman to move on to someone else. SummerSlam is on August 20 though, so WWE still has some time to work with. If the plan really is Reigns vs. Lesnar, they could decide to still focus on Reigns and Strowman for a couple of weeks, then turn to the build for Reigns and Lesnar.