I made seven votes:
Sonya Blade - love of my life to the end!
Jax - where Sonya goes, this man follows. But didn't he die in MK9's Story Mode...?
Shinnok - since we're technically going into the events of Mortal Kombat 4, why should the fallen Elder God be excluded?
Quan Chi - no debate on him.
Tanya - I've been hoping she'd make it as DLC in the previous game. If she doesn't make it to MK10, I'll be quite bewildered.
Reptile - I may hate this lizard, but after Stryker's chapter in Story Mode we never saw any sight of him...I'm smelling a loose end here.
Fujin - he got like only one reference, if I remember correctly...Kratos's ending from the Arcade Ladder. Foreshadowing much?