i personally think it will be raiden seeing that he has a new found hatred towards mortals

dark raiden is with deadly alliance. an 3 vs 1 battle

He doesnt hate Mortals he just hates anybody who puts Earthrealm in danger

I think it will be a new boss awoken after many years of rest by the great war of Armageddon the sole surviver must fight this monster who is curently titled Apocolypse. As for its looks part human part Dragon part Centuar Huge in height ability sumon any dead warrior to his aid

I think they should make an old charactor the new boss. Like Shang Tsung. Like at the end of MKA, he takes the souls of Shao, Goro, Kintaro, Motaro, Sheeva, Quan, etc. leaving him the most powerful charactor there is.

Well seeing that this is the last Mortal Kombat for this Generation of consoles. and a new story will appear...I dont think they will have any of the same characters or bosses. So i think seeing that all the characters and sub boss are in the game. Depending on who the character is...it can follow a story line and depedning on the character they fight different sub boss and boss. Like how street fighter alpha 3 and other games do it now. Try to make it a little different. Because the Dragon King, Shao Khan, Shinnok, Quan Chi/Shang Tsung where all bosses. Or what they can do...is like the choose your distiny was in part 2 and 3...every distiny has a different boss or something... that is what i think.

Shinnok, I have my own reason...but I personally think the course of the MK games was some from the hands of shinnok and he has been behind everything in some way or another. Plus he was around when the One Being was turned into the realms, and he did make the amulet...