Recently, Injustice fans received a "signal" about a new project in the franchise. Several members of the community claim that they managed to meet voice actors who had worked on the games before at the festival.
Allegedly, Phil LaMarr, who voiced Green Lantern - John Stewart, directly stated that he was working on the new Injustice 3.
George Newbern (the voice of Superman), in response to a comment about his work on MultiVersus, allegedly said that he is now working on the third Injustice.
Usually, actors sign an NDA (non-disclosure agreement) when working on such projects, but it is possible that they could have simply "blurted out" (or confused something and are actually involved in something else).