Currently, Finn Balor is feuding with Elias Samson and the two of them are set to battle in a couple weeks at the Great Balls of Fire PPV. However, their feud might not end at Great Balls of Fire. There is a possibility that said feud continues to SummerSlam on August 20th at the Barclays Centre in Brooklyn, NY - although there is also another possibility, one that WWE fans would probably be much more excited to see happen.
Dave Meltzer, speaking on last Sunday's edition of Wrestling Observer Radio, when asked about what the organization has planned for Balor at the second biggest show on the WWE calendar mentioned a couple options for the Demon King including Elias Samson or Bray Wyatt. Although, he didn't sound very certain and also left it open for something else entirely:
"I don’t know where [Finn Balor] would fit in on the show. It could be Bray Wyatt, it could be The Drifter in a rematch, it could be something else."
At this time Bray Wyatt seems to also be lacking an obvious foe for SummerSlam so that could make sense to start something up between him and Balor. This is also a match that had been teased back when Balor had just returned from injury but the match never came to fruition.
A match against Wyatt would be a bigger draw than a second go with Samson and with SummerSlam being the second biggest event of the year for the WWE they will want to make the show as big as possible.
Other options are Samoa Joe or Brock Lesnar, but those aren't very likely. Neither is it likely that Finn will enter the Universal Title picture until after SummerSlam.
One thing we do know is that SummerSlam will feature Roman Reigns challenging for the title - which, we assume, will be against either Samoa Joe or Brock Lesnar after Great Balls of Fire on July 9th at the American Airlines Center in Dallas, Texas.
That is how things stand at the moment heading into the next few PPVs. However, as any WWE fan knows, things can always change so where Balor ends up at SummerSlam is definitely, at this time, not set in stone.