There's a bit of backstory to all this, so please give me a bit to explain. I promise it'll all make sense at the end!
Bosslogic is an artist that has been sharing some interesting Mortal Kombat art lately. Bosslogic has been imagining Mortal Kombat characters portrayed as celebrities. He's had a number of interesting choices along the way, one of which was John Cena. Bosslogic created a piece of art showcasing Cena in the role of Stryker, to which Mortal Kombat co-creator Ed Boon responded by retweeting/saying it was good casting. Everyone thought that was the end of it, and we moved on.
Here's where things get interesting. As you can see above, John Cena has posted another piece of art of him as Stryker. This is a different piece of art from what Bosslogic did. For those who don't know, Cena loves posting up random/cryptic images on his Instagram account. These pictures always apply to something going on in his life, or with people in general. With the posting of this image, either Cena is aware of the chatter from fans about Bosslogic's artwork, or there's something more going on here.
Now let's look back on a comment Ed Boon made a few weeks back about characters in Mortal Kombat 11.
"Our faces, our actors -- we find, you know, real people to scan their entire face. It's not a 3D model, you know sculpting a nose, sculpting a face, stuff like that, it's actually real people. And we have -- I'll tell you this -- we have a huge, huge surprise coming up for a face you're going to see in Mortal Kombat."
Now some might think this pertains to Ronda Rousey, as she was revealed as the voice actor for Sonya Blade. The thing is, that's all that she's providing. A quick look at the character model for Blade shows that Rousey's likeness was not used in-game. That means we're still waiting on the reveal of that 'huge, huge surprise.' With all this evidence floating around, I'm putting my money on Cena!