For a while, it seemed as though NetherRealm Studios had created a pattern of development for itself, switching between Mortal Kombat and Injustice entries every few years. Recently, Ed Boon, the studio's creative director, suggested that the developer may be working on a different project altogether, saying that there was "a reason" the developer broke its pattern.
Despite this, some fairly trusted leakers have come out and claimed that Mortal Kombat 12 is certainly still in the works, even suggesting that Mortal Kombat 4's Reiko will appear as a villain. With the tremendous success of Mortal Kombat 11, and its Ultimate DLC, it seems only natural that a sequel would be on the way. While it may be a few years before it releases, Mortal Kombat 12 should look to some of its previous entries when building the game's roster of iconic fighters.
Ermac
Originally believed to be a secret unlockable character in the first Mortal Kombat due to a shortened version of the message "Error Macro," Ermac made his first proper appearance in Ultimate Mortal Kombat 3, donning the iconic ninja robes in a red and black variation. A culmination of all the lost souls in Outworld, Ermac has been a staple of the Mortal Kombat franchise for 27 years, appearing as a playable character in 10 games.
Unfortunately, Ermac didn't quite make the cut for Mortal Kombat 11, but did appear as a brief cameo, being thrown over the side of The Pit and impaled on the spikes below. Though Ermac tends to side with the villains of Mortal Kombat, he technically isn't an all-evil character, and only wishes to side with those who will give Outworld the best future.
Ermac is also pretty well known for brutally ripping off Jax's arms, which explains their cybernetic appearance in later Mortal Kombat games. Ermac's telekinetic powers and soul manipulation abilities were sorely missed in Mortal Kombat 11, and would make a great addition to a sequel.
Kenshi Takahashi
The blind samurai, Kenshi Takahashi definitely deserves a spot on the Mortal Kombat 12 roster. Though he's physically blind, Kenshi uses his ancestors' spirits to guide him, and has incredibly heightened senses that allow him to see his opponent's moves, sometimes before they do.
Kenshi first appeared in Mortal Kombat: Deadly Alliance, and can often be seen to team up with Sonya, Jax, and the rest of the Special Forces team, where their common goal of wiping out the Red Dragon clan drives him forward. While Kenshi is highly skilled in martial arts and swordplay, he also possesses telekinetic and physic abilities, which allow him to lift opponents, and teleport behind them.
Takeda Takahashi
The son of Kenshi, Takeda Takahashi is fueled by the same rage as his father. Trained by Hanzo Hasashi, one of the bearers of the Scorpion mantle, Takeda works with his father to eliminate the Red Dragon assassins that killed his mother. Takeda's Shirai Ryu training makes him a great asset to the Special Forces, and leads him to being an instrumental part in Shinnok's downfall.
During Takeda's one and only appearance in Mortal Kombat X, he makes great use of plasma-infused swords, and two bladed whips. Though he's not quite as powerful as his father, Takeda does also possess some telekinetic abilities, which he uses in battle to teleport around the arena.
Goro
A 4,000 year-old half-dragon, half-human, Goro has been a part of the Mortal Kombat franchise since the very beginning. The very embodiment of physical prowess, Goro has been Shao Kahn's champion for over 500 years, consistently winning the titular Mortal Kombat tournament.
In his playable appearances, Goro has often been pretty unbalanced, with his attacks doing much more damage than the rest of the roster's. Because of this, Goro has occasionally been restricted to just an NPC boss fight, like his appearance in the 2011 Mortal Kombat reboot.
Modern playable appearances of Goro have chosen to balance him by keeping his damage high, but lowering his agility, making him a slow-moving tank. Goro is also capable of throwing fireballs from his hands and mouth.
Smoke
Though he has often appeared as one of the cyborg ninjas, right alongside Sektor and Cyrax, Smoke has also been playable in his "human" form. In Mortal Kombat (2011) it's revealed that Smoke is actually an Enenra, a demon made from vapor.
These demonic abilities manifest via Smoke's teleportation, and invisibility powers. Smoke can both use his vapor powers to move around the arena, and launch projectiles at his opponent which teleport them closer. He may be a little infuriating to play against, but Smoke's abilities are always very fun to use, and Mortal Kombat 12 could always use more characters like that.
Sektor/Cyrax/Cyber Sub-Zero
While they appeared as NPC opponents in Mortal Kombat 11, all serving Kronika's Cyber Lin Kuei army, Sektor, Cyrax, and Cyber Sub-Zero haven't been playable since 2011's Mortal Kombat, aside from the Triborg amalgamation in Mortal Kombat X. Though they're all essentially just color-swapped models, these cyber ninjas each have their own set of unique abilities.
Sektor's main gimmick is his ability to launch homing missiles at his opponents, and use a flamethrower, while Cyrax can fire a restraining energy net and a lethal buzzsaw from his chest. Cyber Sub-Zero, on the other hand, boasts most of the same powers as his human counterpart, but fires projectiles at a much faster rate.
Cameo Characters
Over the last few Mortal Kombat entries, more and more cameo characters have started to filter in via DLC. Mortal Kombat 12 will likely be no different, and if some of the rumors are to be believed, Mortal Kombat 12 might even bring some old cameo characters back to the roster. If NetherRealm was to do this, there are a few fighters that would make great additions.
The PS3 and Vita-exclusive Kratos would make a great returning cameo character for Mortal Kombat 12, and could feature an all-new moveset and appearance based on the more recent God of War entries. Both the Alien and Predator from Mortal Kombat X should also make the jump over, as their movesets were some of the most varied and satisfying in the entire game. Freddy Kruger and Jason Vorhees would also make great additions for horror fans.