WARNING: The following contains spoilers for Action Comics #1035, on sale now from DC Comics.
As Superman prepares to leave Earth for a showdown with the cosmic despot Mongul after dealing with several of his associates throughout the DC Universe, he is going in at a disadvantage, with his powers noticeably beginning to diminish after being exposed to extra-dimensional rift at the start of the Infinite Frontier era. However, the Man of Steel isn't going into this confrontation alone and, while the Justice League remains on Earth, he has brought in different reinforcements with the latest iteration of the Authority from the concurrently published miniseries Superman and the Authority.
Grant Morrison and Mikel Janin's story is presumably set on another Earth, with Superman surfacing on this world sometime around the Kennedy Administration in the mid-20th century. While providing passing references that he was transported through time and space, the older Superman finds himself on a world that features reimagined characters from the DCU and WildStorm Universe and sets out to form a new version of the Authority to save humanity from itself when his previous efforts as a solo superhero and heading the Justice League have failed. Due to its alternate history approach and visibly different Superman, there was speculation that the miniseries was outside of main continuity though Action Comics #1035 -- by Phillip Kennedy Johnson, Daniel Sampere, Adriano Lucas and Dave Sharpe -- reveals that the miniseries is more connected to the main DCU than initially believed.
After Mongul's associates spread their activity to Earth, including a brazen attack on the Fortress of Solitude, Superman realizes he has put off neutralizing Mongul for far too long and resolves to head off his enemy at the source from Mongul's throne world of Warworld. While Batman confides in his old friends that he has noticed that Superman's powers are fading, Superman points out that he has the situation well in hand. After one last romantic night with Lois Lane, Superman meets back up with the version of the Authority he has assembled in Morrison and Janin's story, with the team transporting itself to Mongul for the epic showdown for the fate countless worlds.
Apart from Superman's comments on being transported to this alternate WildStorm Universe through a vortex, there have been other clues that the two universes are connected. Both stories feature a Superman whose powers are steadily failing him though Superman and the Authority suggests this may be due to the Man of Tomorrow's advancing age. The miniseries' presumable main antagonist Ultra-Humanite makes it clear that he is aware Superman has a superhero son elsewhere and intends to deal with Jon Kent after he defeats the Authority formed to stop him. Morrison, for their part, acknowledged that Superman and the Authority would tie into Johnson's Action Comics run, without going into specifics.
The biggest lingering question about Superman and the Authority is how Superman got to this alternate world and how he returned to the main DCU, no longer as aged as he appears in Morrison and Janin's story. In the meantime, Superman may have apparently thwarted Ultra-Humanite in the alternate world but has bigger concerns to worry about as the threat of Mongul looms ahead of him and the Authority while his powers continue to diminish. And if Future State offered any insight on how this showdown goes, even Superman's reinforcements from another world may not be enough to save the day this time.