They've said two minimum with the possibility for more or even for DLC finishers.

We've even seen three Fatalities for Sub-Zero already, if his classic spine rip seen on GTTV is actually in the game.

Sweet. Hopefully than they can include all the classic Fatalities and have some room to put in new ones.

I've seen the spine rip but not SZ's other fatalities in this game. What are they?

One is he freezes the opponent from the waist-down, then does a torso rip and holds them up with intestines dangling out.

The other is he rips the spine and skull out through the stomach, freezes the rest of the body, then swings the spine-skull like a mace to shatter the body.

That second one sounds cool, smashing the body with the head.