There really isn't much to back it up.

Well, according to Ed Boon the boss will be a returning character you wouldn't expect. I would say that would eliminate the obvious baddies of Shang Tsung, Quan Chi and Shao Kahn. Looking at the stories and motives of other characters, I think the theory of Havik creating a time rift is plausible. In fact, I think Havik would be more likely to be behind the scenes stirring things up than most of the other characters throughout the series.

But you know, Reiko's been awfully quiet for awhile now, too...just sayin'.

Nah, Liu Kang is comming back to bite back Raiden for being so dumb.

I can see this happening! Would actually like this.

Another theory that I have is that Raiden goes fukin mad after the incidents of mk9 and becomes an evil villain.

I'm actually shocked that Shinnok won't be the final boss as everyone was assuming.

I'm going to second this. I can see Raiden becoming a mad nut after realizing what he's done in the past and just goes stir crazy about it.

It sorta makes sense seeing how he just blatantly zapped Liu at the end. I mean he DIDN'T have to do that and yet he did. I guess that could have been like the final straw or something?

The final boss ....? Ha thats easy it'll be the last guy u fight

Nooooooooo Liu Kang! However, if he is in then, I'll have to settle.

What if Raiden becomes the final Boss???

I would like for Shinnok to be playable

Yeah I agree! They could easily use the ending of MK9 to explain his journey into the darkness. A demented thunder god sounds like a badass boss IMO.

I also like the idea of Liu Kang as a villain. Would make Kitana's story even more rich.

I'm guessing Shinnok or evil Raiden depending on what character you choose

These Raiden and Shinnok as final bosses would be too predictable. So Havik would be a nice change.

I don't know if Havik will be back, but I hope so, Havik is the embodiment of badassery.