Yes they did say that every character would make an appearance. I'm not sure about these ones that you mentioned since they really aren't mainstream. Blaze either. C/Khameleon i think is only a charcter that transforms into other characters. Meat did have a back story that i read along time ago. He was a practitioner of the dark arts and brought back to life by quan chi. Mokap was just a motion capture guy. Blaze is just a protector of the egg. I think every other secret character had a developed story and made an appearance in various mk games. I think the four here are just crap thrown together to make it seem like some secret. But either way, the only way to really find out is to wait and see.

They may be in it but I doubt very much that every character from every mk game will have storyline to them. Its early days yet I could be wrong but its a lot of work to do for old characters that are not going to be even playable in the game itself.