The news about Injustice 3 is not good, according to a leak by an insider. Since this is a journalist, it doesn't mean it's definitive, but this is someone close to NetherRealm. Jeff Grubb discussed the possibility of Mortal Kombat 12 being delayed for the series.
If NetherRealm goes back to Mortal Kombat instead of Injustice 3, it will most likely NOT be 12. An old tweet from Ed Boon suggests they are working on Shaloin Monks. I think the reasoning behind Injustice 3's supposed delay is sound but still untrue.
Injustice 3: Release Date, Leaks & Everything You Need To Know
Will Injustice 3 be delayed?
Maybe. Just maybe.
The reasoning is below in the video, but it's basically an effect of the strife going on with DC. As a result of the split between Warner Media and Discovery, many are unsure what will happen with the DC IP. However, I have heard from a friend who recently left TT Games (a subsidiary of WB Games) that this split will not affect the games studios.
More Injustice 3: Injustice 3 May Have Been Leaked Through An Update In Injustice 2
A similar website recently used a journalist's theory as evidence and then told readers not to take it literally. That's what we need to do with this information. This is a guess by a journalist, and even he admits that he is guessing.
It's been taken as factual, even though it's not. At this point, we are all just guessing. I will keep you updated if any concrete proof is found.
Otherwise, don't assume this is true at all.