Mortal Kombat 1 is not only about fighting, but also about a deep story. The developers are not finished with the story yet and are ready to introduce something new
It turns out that NetherRealm Studios intends to introduce more than just DLC with fighters for Mortal Kombat 1. Ed Boon has confirmed that a story expansion will be released for MK1.
The developers have already had similar experience, for example with Aftermath for MK1 11. After this story DLC, some kind of “big surprise” is expected, but NetherRealm is in no hurry to reveal everything.
They intend to support Mortal Kombat 1 longer than MK 11.