Gene Lueng Yang's well-received Batman/Superman run is being cut short, as DC has announced his run - and the series - will be ending with September's Batman/Superman #22.
"Mr. Mxyzptlk resurrecting Calendar Man from his death during A-Day is causing some reality-rattling consequences," reads DC's description of Batman/Superman #22. "If Superman and Batman are going to prevent a fifth-dimensional god-being from compartmentalizing all of existence, they’re going to need to turn to some unlikely allies."
A-Day is a recent event that occurred in Infinite Frontier #0 where the Joker seemingly launched a deadly chemical attack on Arkham Asylum, killing many people - prisoner and worker - alike. Calendar Man, a bit of a regular inmate there, was among those dead.
It's unclear how Calendar Man returning could have "reality-rattling consequences" given he has no metahuman powers that we know of, but with Mr. Mxyzptik involved - who has "reality-rattling" metahuman powers and then some - everything is up for grabs.