Mortal Kombat 11 apparently still has a lot more content in the works before developer NetherRealm Studios decides to move on.
The thing to note is that Mortal Kombat 11 being data-mined for clues is not something new. The game has been data-mined a number of times since release and that too for accurate predictions.
The recent Aftermath story-based expansion and its three playable characters (Sheeva, Fujin, and RoboCop) were already data-mined ahead of the official announcement. The new Kombat Pack 2 which will soon add three more characters (Rain, Mileena, and John Rambo) in Mortal Kombat 11 was already unveiled similarly ahead of time. Those same data mining episodes, including more recent ones, now lead (via EventHubs) to the existence of another story-based expansion as well as a new Kombat Pack 3 for the game.
There are still five more character slots remaining to be filled, according to data miners. Aftermath and Kombat Pack 2 added six characters combined. A new story-based expansion and Kombat Pack 3 are hence believed to add the remaining five.
As for which playable characters remain to be announced; breadcrumbs point towards Havik and Daegon to be part of Kombat Pack 3. Sareena was once rumored but is now believed to have been scrapped. Ash Williams from the Evil Dead franchise could possibly be the last guest character for Mortal Kombat 11 and who should accompany Havik and Daegon in Kombat Pack 3.
On the other hand, characters like Quan Chi, Takeda, Shinnok, Taven, and Reiko will supposedly have some role to play in a second story expansion pack. If what data miners are saying is true, NetherRealm Studios will be picking two characters from that lot for the playable roster. Fans though will probably be betting on Reiko who has been a highly requested character since his debut in Mortal Kombat 4.
These are all rumors though without any official acknowledgements; except that the same was being said until Aftermath and Kombat Pack 2 were unveiled. NetherRealm Studios is believed to be working on Injustice 3 for next-generation consoles in 2021. The developer appears to be finalizing a last update for Mortal Kombat 11 before moving on.