The plan right now is still for Brock Lesnar to face Roman Reigns again, according to the Wrestling Observer Newsletter, though obviously plans can change.
The “contractual snag” storyline with Brock Lesnar is just that – a storyline. WWE appears to once again be trying the same angle they tried before WrestleMania, where they try to make people hate Brock Lesnar in order to get them to get behind Reigns. This obviously turned out to be a horrible strategy last time since it didn’t get fans to like Reigns and instead just got them to turn on Lesnar, which resulted in the crowd booing their match relentlessly.
If the Lesnar vs. Reigns match happens again at SummerSlam, it seems pretty likely that it will get an equally terrible (or possibly much worse) reaction from the Brooklyn crowd, which is always “rowdy.”
Though a Braun Strowman cash-in during or after the match would probably get a big pop and send the crowd home happy.