In the latest Wrestling Observer Newsletter, Dave Meltzer referenced the rumors about SummerSlam getting a guest host and a WrestleMania-worthy main event.
Meltzer noted that the leading rumor is that the show will be headlined by Roman Reigns vs. John Cena for the Universal Championship.
The latest on Cena is that he and WWE were in talks and as of last week in regards to an appearance on the July 16th episode of Friday Night SmackDown in Houston but nothing was finalized.
Meltzer added that people in the company have been talking about Cena vs. Reigns as the big SummerSlam match but it has not been confirmed. Andrew Zarian alluded to this on the Mat Men Podcast without outright saying that Cena vs. Reigns was the plan.
WWE plans on running in an NFL stadium so it makes sense to put on a WrestleMania-caliber match. If they can’t agree to terms with Cena then perhaps, they could work out a deal with Brock Lesnar. The Rock would also fit the bill but the assumption is that Rock vs. Reigns would be saved for WrestleMania. Bill Goldberg could be a possibility as well.
As far as the guest host rumors, the Mat Men Podcast hinted that it would be a big name but there were no other hints given.