From their official MK11 Ultimate Twitter account:
They have announce they are working on a new project and video game. Is it Injustice 3, a new Marvel tag game, Mortal Kombat: Shaolin Monks 2, MK9 remaster, old classic MK game remaster, 3D MK games remaster? Who knows. But now we all know that MK11 will no longer be receiving any buffs / nerfs or new characters as NRS is going to be focusing all of their energy, time, and resources into their new upcoming project.
Good news? Bad news? I guess it's up to you to decide.