Three of the four bios were revealed in E3 just yesterday by MK Online. The only one missing is Jax.
Frost
I made my move to seize control of the Lin Kuei from Sub-Zero. He had let his guard down and I took the Dragon Medallion from him. I could feel its power coursing through me! That is the last thing I remember. I awoke in this tomb, surrounded by frozen corpses. I must still be in Outworld. The medallion is gone. No doubt Sub-Zero took it from me and left me here to die. He will pay dearly.
Kitana
For thousands of years I have fought skilled warriors, each new one seemingly more advanced than the last. But this….Dragon King…was a more powerful foe than I had ever imagined possible. He resurrected me from death and enslaved my soul. I had no choke but to kill in his name.
Blaze
For millenia I existed for one purpose…to monitor the strength of the world’s kombatants. My creator foresaw a time when warriors would become too powerful and threaten all of existance. I was to sound the call to awaken her sons when the apex was drawing near. Their actions would determine the fate of these superior kombatants and ultimately prevent Armageddon. It seems, however, that one brother has been prematurely revived.