Shinnok has to be in. The costume is so awesome! Plus if you look at Raidens costume in the trailer while he's using the amulet on Shinnok, it looks like he has a different costume. It could be like a flashback while Raiden is telling a story about how he had to banish him to the netherrealm. Raidens costume in that clip looks mk1ish. There's not enough proof in that trailer to show shinnok is or isn't a playable character. Just speculations

Nicely brought out. But one can simply say if he's plays that huge of a role in the story to the point where they feel like they need to give him a completely new redesign, then why stop there? Why not just go ahead and make him apart of the roster? I mean it would be odd to not have a "major player" -as you put it- be apart of the roster or at least an arcade boss/sub-boss.

Rather he's playable or not- I just don't see Shinnok as being story mode only. Not at all. At least I expect him to be an unplayable boss but even that I doubt. I'm betting he'll be playable.

I'm thinking he's playable but on the main roster is hard to say. It's a good possibility but he looks good because he has to, he's in a cutscene.
I'd like an overpowered shinnok that requires a title screen code to get on the roster lol. The one that nearly destroyed earth.

To have new challenges on the hour, my guess is that we'll play everyone we've seen so far. I'd like to see some hourly tower where you work your way up the black dragon or Lin Kuei food chain with the fat henchman. I also wouldn't be surprised to see some unlockable or hidden characters with one variation or a combination of special moves from others. Maybe frost with a few kitana and sub moves. That would be pretty awesome.