At this point, there's really no doubt the Justice Society of America is returning to the DCU, but the question is…how?
If Jay Garrick's brief appearance in "The Button" crossover tells us anything, it's that the Justice Society is probably trapped in a manner similar to what happened to Wally West – unable to return to existence unless someone remembers their names and serves as a tether to the new, constantly morphing timeline.
But in "The Button," Barry couldn't remember Jay, so the original Flash's attempts to come back to the DCU were thwarted.
As Barry and Bruce were reflecting on what just happened, Barry theorized that Jay needs a different "lightning rod."
As readers have already seen, in DC Universe: Rebirth #1, Barry Allen was Wally West's lightning rod. But this issue seems to imply that Barry is not a similar tether for Jay Garrick.
So who is?
Although Bart hasn't been part of the "Rebirth" initiative, this might be just the opportunity DC needs to reintroduce him. Whether he shows up from the future like Saturn Girl has (which would align with his former origin) or he is a regular kid in Rebirth who starts to have memories of his former self (like some of the Titans, Bart could serve as a lightning rod for Jay because of their previously close relationship.
Jay served as a mentor and, for some time, an actual guardian when Bart lived with Jay and his wife Joan for several years.
Joan Williams Garrick
Speaking of Joan, it would probably make more sense for her to serve as Jay's tether to the "Rebirth" era. The two were among the most popular of DC's earliest married characters, and after their marriage, she was portrayed as an important supporter for her husband.
However, there's been no indication that Joan Garrick exists in the "Rebirth" universe. And with Jay Garrick looking like an older man in the brief appearance shown in The Flash #22, it would make more sense that Joan was already married to the man and is trapped in the timestream with him.
Plus, if Wally West's interaction with Linda Park is any indication, being married to a speedster in another timeline doesn't make you that character's lightning rod.
So if we follow the reasoning that a Flash has to bring back another Flash (as Barry brought back Wally), then maybe it's Wally's turn to inspire the rebirth of a speedster.
And since he was never part of the "New 52" universe, and seems to have hopped into "Rebirth" from his life in the post-Crisis universe, he would theoretically be the most likely character to remember Jay. In fact, in DC Universe: Rebirth #1, Wally most definitely remembered the Justice Society, as he was shown watching Johnny Thunder and talking about the history of the JSA.
Plus Jay was an important mentor for Wally during the years leading up to the "New 52," particularly before Barry's own return from the "dead."
But if we hone in on the current story of the Justice Society of America, there's one key player who emerges as a probable lightning rod for Jay — and for that matter, all the JSA members: Johnny Thunder.
He remembers the Justice Society, and he's already part of the "Rebirth" era.
The character, whose origin can be traced all the way back to the Golden Age of comics, was shown remembering his friends from the JSA in both DC Universe: Rebirth #1 and The Flash #21, DC's second chapter of "The Button."
The character, best known by modern comic book audiences for his time in the Justice Society of America, keeps showing up in all the "Rebirth" teases plotted by Geoff Johns, who is probably going to be handling the return of the Justice Society. (And as JSA fans know, he's a good person to do it, having written the team for more than 100 issues over 10 years).
Or perhaps Jay Garrick's connection to the present-day DCU will be more related to the future while tying in to the former role of the Justice Society as trainers for young heroes.
For example, when DC Universe: Rebirth #1 said that Johnny Thunder has a great-grandson who believes his rants about the Justice Society, many fans wondered if the boy could be Jakeem Thunder. The character, written for many years by Johns on his JSA team, had possession of the powerful Thunderbolt and was a fan-favorite young DC hero. If that's the great-grandson's name, and if he really does remember (or believe in) the JSA, he could serve as a lightning rod for not only Jay, but the whole team.
Or any other unsuspecting young hero in the "Rebirth" universe might begin to have memories of their former life in the Justice Society. From Billy Batson to Courtney Whitmore, there are any number of young heroes that DC fans would love to see involved in the return of the elder JSA members.