Since the hidden characters have NO BIO OR ENDINGS.... they will probably be DA characters, plaed in the game for no reason. That way, they get a bigger roster w/o working on a new character. So let's say Raiden and the heros are trapped. Maybe Raiden and Jax are amongst those hidden characters. My guess is the characters that we almost always see like Johnny Cage, Sonya, Kung Lao, Jax, Raiden, etc, will be in the game. I still think Jax and Raiden will not be on the select screen, and will be hidden. Confirmed to be in the game is not the same as confirmed on the select screen.

I think that these characteres might make it as secret characters.

Mavado
Nitara
Jade
Fujin

I have a strong feeling about Rain making it as a secret character that you unlock from Konquest, after seeing that interview with that guy who mentioned Rain. I know he said that you see him in Konquest, but it's odd for them to mention a pointless character like Rain out of the blue, if he is not in fact included in the roster.