So Boon posted this still from the movie Big:

Hint

Some have voiced guesses of him hinting at Mileena, Motaro, and Shang Tsung. A couple have (weirdly) even guessed at Nightwolf...

It's certainly a hint for someone, and I'll give you a hint- it's not Nightwolf!

This is Zoltar (as seen in Big):



Here is Shang Tsung (as seen in MK9)



Hmm there’s some similarities between the two of them; facial hair, colouring of clothing, an amulet. Is that it though?

No. We all know Boon, he likes to have us guessing at hints (and even when there actually isn’t a hint at all); some are obvious like the image of a moon hinting at Reptile, and others need a bit of thinking beyond what’s in sight. So with the latter in mind- let’s look at the bigger picture here...

This is part of the plot taken from the Big wiki:

Josh runs into the company's owner, Mr. MacMillan, at FAO Schwarz, and impresses him with his insight into current toys and his happy-go-lucky, childlike enthusiasm. The two play a duet on a foot-operated electronic keyboard, performing "Heart and Soul" and "Chopsticks." This earns Josh a promotion to a dream job: getting paid to test toys.

BIG Wiki

Should we look even more outside of the box...? Yes of course we should!

“Heart and soul” this is obvious actually- Shang steals souls, and in MK9 we saw his soul put into Sindel by Shao Kahn, and where on Sindel does his soul show as it’s transferred? Her heart!

Keeping with the song thing for a moment... “Chopsticks” chopsticks are from China, and what does China have to do with Shang Tsung, other than his outfits looking Chinese?

“Shang Tsung (originally named "Shang Lao") was based on the Chinese sorcerer Lo Pan from the film Big Trouble in Little China. A character named "Kitsune", which was later developed into Kitana, was going to fit into the story as Shang Lao’s (Tsung) princess daughter - the spoil of victory for winning the tournament, who would betray her father after she fell for Liu Kang. Mortal Kombat art director Herman Sanchez said that as the series progressed he decided to emphasize Tsung's air of "sinister regality."

Shang wiki



Then there's also the fact that an ally of his, Reptile, is confirmed; Liu Kang is very likely to return, and Goro, Shang’s protégé is already known to be Pre-order (DLC) for the game.

But wait... Do we even need Shang Tsung?

Isn’t Quan Chi replacing him now? Oh and Shinnok, remember he’ll probably be a big part of the games story (even though Quan Chi is clearly using his skull as an accessory on his armour!); so between Quan Chi & Shinnok we don’t really need Shang Tsung.

Well what if I told you that although we may not need Shang, it’s increasingly more likely he’s going to be in MKX and that it’s possibly him who’s the surprise returning boss:

“According to GamePro magazine in 1993, the MKII version of Shang Tsung was nineteen years old, and an article about the game also included a rough sketch by Mortal Kombat co-creator John Tobias of Tsung's "true form," a twisted demon, which has never actually appeared in the video games”.

Now alright, the Wiki is wrong because it wasn’t 1993, the magazine was published in 1994, but still... The demon form shown in this scan of the actual page from that same Gamepro magazine (from 1994, get your facts straight Wiki!):



Plus let’s not forget the GameStop instore ad for MKX which started running in January and mentions Shang Tsung.

Gamestop ad

Oh and the tweet from December 11th where Boon actually sneakily confirmed him:

Link

Now let's sit back and wait for ol' Shang to be revealed; soon, soon.