Mortal Kombat 1 will no longer be supported
NetherRealm announced that no more story and character updates will be coming to Mortal Kombat 1.

Developer studio NetherRealm has announced that it is ending support for Mortal Kombat 1 in order to "move on to the next project". This means no more DLC, characters or additional story chapters will be coming to the game. Updates after today will be aimed at balancing the game or fixing minor bugs.

Mortal Kombat 1's Story Ends
The studio shared the update on social media, stating that it "may have been disappointing" but was necessary for the studio's next step. The studio's full post is as follows:
"We hear players' requests for continued game support of Mortal Kombat 1, and while we will continue to support Mortal Kombat 1 with balance adjustments and fixes, no additional DLC characters or story chapters will be released beyond this point.
We realise this will be disappointing for fans, but our team at NetherRealm needs to focus on the next project and make it as great as possible."
It's not a big surprise, though, as fans had already surmised that MK1 would no longer be supported with the release of Mortal Kombat 1: Definitive Edition on both PC and console platforms in recent months.
NetherRealm has yet to officially announce what its next project will be. However, fans agree that this will be the sequel to the beloved DC fighting game series Injustice. There is no clear announcement about Injustice 3 from the publisher and developer.
Source:
https://www.eurogamer.net/netherrealm-ends-mortal-kombat-1-support-as-focus-shifts-to-the-next-project