I have to side with [MENTION=17841]GloriousDK[/MENTION] on this. There is absolutely no guarantee that Liu Kang is in the game, but between the Living Towers figure looking more like him than it does any other character, his Italian VA saying that he's done some voice work as Liu, all other good MK1-2 characters being back, and Liu having such a huge beef with Raiden in MK9 - a storyline that is obviously going to be pursued further in MKX, as per Sub-Zero's claim that "Earthrealm deserves a better protector" - while we're still missing a "fun, surprise returning" final boss, we're looking at a growing mountain of circumstantial evidence.
It's one thing to say that "Liu Kang could still not be in the game," which is true, and it's another to say "it's unlikely that Liu Kang is in the game." No, it's likely that he is. And I don't even like the guy.