Honestly I can see it being Liu kang he died and becomes a soul so enraged that quan chi can't control him he kills both quan chi and shinnok and takes over the nether realm army to exact his revenge and ends up taking a war upon outworld and earthrealm that lasts 25 years and ends up hosting the mk tournament and becoming a mad power hungry fire god and has become what he hated in Shao Kahn

I realize that having Shinnok as a boss character wouldn't really be moving on but Boon said it will be a recurring character so with that in mind I find him most appropriate for a number of reasons;

First, he got rid of most threats by the end of MK9. Both Kahn and Liu Kang are out of the picture which means he has only Raiden to deal with if Quan Chi doesn't betray him. Second, he has an army to invade earth at any time. Third, he is an elder God which pretty much qualifies him for a boss character and as mentioned by Chrome, he was a terrible boss character in MK4 which means that they can change that this time around. I think Shinnok definitely has potential, gameplay, story and design-wise. With all that in mind, it makes a hell of a lot more sense to have him be the main antagonist rather than Raiden or Kang.

I know its not very likely since Boon stated it will be a character no one will see coming, and if it were up to me I'd have gladly welcomed an entirely new boss character. I just hope its not an anticlimactic boss character that wouldn't really do this game justice like, you know, Dark Raiden or Crisp Liu Kang

Boons comment meant without any hindsight of his cryptic comment so I think its Liu Kang or Dark Raiden for sure. The expectation would be the Shinnok, Dragon king era bad guys or recurring ones such as Quan chi, kahn, tsung etc.

The game will probably span the Shinnok and dragon king arcs over the 25 years so those characters could appear as Lesser bosses like Shang tsung,kintaro, goro etc did in the previous games story mode.

May be Ermac with king Jerrod's soul commanding ;)

Why would anybody want this?

It'd ruin the one premise that Ermac's entire character is based on.

I want it to be Shinnok non-playable character. or the last dlc character that they release...

You're all so stupid. It's obviously Jarek.

im saying it first, its either Shujinko or Daegon

What if the surprise boss is Shinnok? If it's supposedly someone we won't see coming, what if Ed said that just to throw us off, only for it to be the obvious choice after all? Then he'd be right that we wouldn't see it coming.

I'm gonna throw my money in the "Liu Kang is the big bad' bandwagon simply because Ed probably thinks he's being more sly than he is, and because of the new, angrier-looking dragon logo that's kind of always been synonymous with the imagery of the MK tournament champion.

Boon being Boon, of course, he'll probably make it Hornbuckle.

Shinnok.
Technically speaking, Shinnok is the least expected character right now. It would be the surprise Ed had promised after it turns we all waz stopid n it waz obvs

Maybe Kitana, Sindel's daughter. Going out on a limb to say or maybe Fujin.

That's actually pretty clever.

Everyone's overlooking Shinnok under the assumption he will not be the boss.

I wonder if Ed Boon knew this.

Alex Jones.

Since the story spans over 25 years, have you guys even considered that there could be multiple end-bosses? Like, Shinnok, Onaga, Blaze and maybe someone completely new as well.

it doesn't look like he will be big boss, but i'll be disappointed if Shinnok is nowhere to be seen.

Best answers so far:
Evil Liu Kang
Zombie Liu Kang
Krispy (Kreme) Liu Kang
unambiguous Liu Kang
Liu Kang's dragon form
Liu Kang's soul
Liu Kang's baby brother benny
Liu Kang's dog
Dark Raiden
Shinnok
Quan chi
Reiko
Scorpion
Noob
Noob-Smoke
Noob-Sindel
Noob-Liu Kang
Noob-etc
Meat
Mileena
Mokap
Goro
Superman
Havik
Hornbuckle
Shujinko
Onaga
Art Lean
Reiko
Jarek
Zebron

now for my suggestions:

Solomon Grundy
Wonder Woman
Cyber Sub-zero
Cyber-Noob-Smoke-etc
Cyber anyone
Sareena
Skarlet
Tremor (shout out for the Tremor fans)
Statue of Liberty
'Blanche'
Lady Gaga
Mewtwo
Mega Mewtwo X
Mega Mewtwo Y
Pacman
Hachiman
LEROY JENKINS
Great Kung Lao's zombie soul inside Ermac inside Sindel inside Shang Tsung inside D'Vorah inside someone else inside a zombie resurrected by Quan Chi killed by Onaga resurrected by Quan Chi again. (Kombatception)

Bold answer is Raiden. But Shinnok would make sense. I would love to have him playable as his humanoid look but fighting both this look and his demon side during the boss battle could make for a cool, surprising return.

It will be Johnny Cage. He is the greatest actor that ever lived and had everyone fooled by the end of MK9. He will become the Wesker of Mortal Kombat.

Well, you have a good sense of humour, at least.

Might as well make jokes this early since it's all up in the air for the moment.

The big bad could be an 100% unironic Ed Boon on steroids for all we know.

Lol!

It's time for a female big-bad-boss. I'm hoping for Sindel brought back from the dead (again).

Reptile. He's done being a doormat!