So, Johnny Cage is referred to as "Raiden's Champion" in the latest MKX comic, and Kotal Kahn seems happy to work with him. At this point, I think that means that he's in the game, because he's gonna end up dead in the story in an important way.
While we know that everyone who Sindel killed ends up in the Netherrealm (and controlled to some degree by Quan Chi like Kitana & Sindel are in the trailer). What we never see in MK9 is what happens to Liu Kang after he's killed by Raiden. My working theory at this point is that the Kamidogu in the comics are introduced, because Quan Chi is attempting to use them to revive Onaga (
who was seen in Raiden's visions in MK9), as he's the original ruler of Outworld and using him as a way of taking it over, once Mileena's weakened Kotal Kahn's grasp on keeping order there.
As the Dragon God was someone who had a burning and limitless hatred of Shao Kahn, I'm 99% certain that Quan Chi is going to use Liu Kang as the vessel to revive Onaga into -- especially since Raiden won't have what it takes to face Liu Kang again. He's a champion of Mortal Kombat and an amazing fighter, and it's not only demoralizing but it's a brilliant tactic, because at this point he could essentially pull off the same thing that he did with Scorpion, but to a level of cosmic power and influence. That's the other reason that I think that Johnny Cage as Raiden's Champion means that he's guaranteed to kick the bucket, and push Cassie further into the main role of the series moving forward. Additionally, the comics establish that Johnny Cage is Kotal Kahn's number one most trusted ally.
My bet as of now (before the Kombat Kast about the story) is that the final battle will COMPLETELY flip the series on its head, and it'll be the player as Kotal Kahn having to beat Liu Kang in order to save Outworld -- (and thus Earthrealm) from Quan Chi's ultimate plan.