WARNING: Spoilers ahead for Justice League #42 from Geoff Johns, Jason Fabok and Brad Anderson.
You may have heard rumors that Batman would learn The Joker's true identity in today's issue of Justice League.
That's technically true -- mostly because, as has been teased in the October 2015 solicitations, Batman takes on a surprising new role -- that of the God of Knowledge, a role taken from Metron -- in the issue.
When, as the result of a misunderstanding, Metron is separated from his chair, the powerful item is about to Boom Tube itself away, putting the Justice League and Metron at the mercy of Darkseid and the Anti-Monitor, two ancient, powerful and warring forces.
In order to prevent that, Batman launches himself onto the Mobius Chair...and is immediately subsumed by it, becoming a New God. Along the way, he asks the chair The Joker's true identity and is both shocked and in denial of...whatever it is. The audience doesn't find out.
It's likely to stay that way, unless revealing The Joker's identity can somehow resolve the plot later. The Joker was just featured in the "Endgame" storyline, his second major storyline in less than five years, and apparently died at the end after what looks to be decades or centuries of functional immortality. Of course, Batman apparently died, too...and look where that got him.
The Batman titles and Justice League appear to be taking place either in different timelines or perhaps on different Earths in DC's multiverse. In fact, status quo changes to a number of major DC heroes have yet to be reflected in Justice League or Justice League America. This includes the "new" Batman, Jim Gordon, and Superman's new "costume" and now-public identity.
The next issue is teased as "Bat-God," a wink and a nod to a fan meme that Batman is often written as godlike, possessing powers and abilities far beyond what his actual character could plausibly possess. While Johns himself is sometimes guilty of characterizing Batman in this way, he's also contributed to humanizing him significantly with stories like Batman: Earth One, in which we see his mistake-plagued early days as a crimefighter. Given Johns' previous forays into meta-textual commentary (see Infinite Crisis and Superboy Prime), it seems likely the "Bat-God" title is an intentional wink and a nod at the audience.