Recently, it was announced that Dwayne Johnson will not continue his tenure as Black Adam in the new DCU anytime soon. It was speculated that the decision was made in lieu of the film's underwhelming box-office performance, especially since there were talks that the actor was set to be one of the major faces of the DC franchise before James Gunn and Peter Safran took over.
A couple of days ago, we learned that Johnson was also invited to make a cameo appearance in Shazam! Fury of the Gods although he declined it due to unknown reasons. Some fans believed that it was a sign that the DC franchise was indeed planning to make Johnson's Black Adam a bigger presence.
Now, according to a scoop from TheWrap reporter Umberto Gonzalez, Johnson also declined to make a cameo appearance in The Flash. Apparently, back when it was filming, Johnson's producing partner Hiram Garcia was asked if the actor can do a cameo in the film. However, he "politely declined" on his behalf.
There were no details provided regarding what Johnson's cameo appearance in the film would have looked like. It is likely that it could be in the same vein as Henry Cavill and Gal Gadot's initial cameo appearances for the film that were now cut in the wake of the recent decisions made in the new DC Studios.
Prior to Gunn and Safran's takeover of the DC franchise, it sounds like Warner Bros. was planning to make Johnson's Black Adam one of the main players in the franchise which is probably why they tried to have him make a cameo appearance.
Since Johnson is no longer playing Black Adam in the new DCU, if he did end up filming a cameo, there is the likelihood that they would have decided to cut his appearance anyway so, at the end of the day, it seems like there is no benefit on adding him in the film even in a tiny part.
The Flash is slated for release in theaters on June 16, 2023. You can check more details about it here.