Scorpion & Sub-Zero was supposed to be "DLC".... Is this true? Any word of this?
No, but someone found references to the DLC characters in the game's source code. Or rather, he said he did, but it isn't known if it's credible or not. His list states that the four DLC characters are Lobo, Batgirl, Zod, and Scorpion.
From what I've gathered, most people believe that his list is fake. Either that, or Ed Boon, being the troll that he is, had the DLC files purposely named wrong to fool us if we found them.
Lobo has already been confirmed to be the first DLC character.
Batgirl is unlikely since she realistically wouldn't play much differently then Batman does. Not to mention that she lost to Power Girl in a popularity poll that Ed Boon had started. Some believe that the "Batgirl" files, if real, are actually for Power Girl.
Zod is entirely possible given that he'll be in the upcoming
Man of Steel movie, but he would likely be very similar to Superman, which is leaving some players skeptical.
Scorpion is ridiculous. NRS said that they wanted Injustice to be recognized as it's own game, separate from Mortal Kombat. Adding Scorpion shits all over that idea. Plus, there's no way in hell that Scorpion could make it in over a character as important and highly demanded as Martian Manhunter. Some believe that the "Scorpion" files, if real, are actually for MMH.
Of course, this is all speculation.