a new cyborg might be possible
That would only work if he's completely new, but new cyborg having moves of 3 old cyborgs sounds more cheesy than old cyborg having extra moves from 2 other old cyborgs.
I will say that hotaru especially seems unlikely, simply because while "unique" he was VERY cliche. I would like to see him done right, but dear god he was boring and predictable.
Picture me an unpredictable inhabitant of Orderrealm (that is not in Resistance to the whole Orderrealm system). Every character from there would be either boring guard/policeman/law enforcer type of character, or a character that opposes basic characteristics of an Orderrealmer rather than represents them.
Concept like this would be fitting for a new Orderrealm character:
http://www.rilmani.org/timaresh/Mercykillers
as well as ways of opposing Chaos
http://mimir.net/factions/mercykillernumbers.html
Tremor- I'll be honest in that grappling ninja might be interesting, however I still really don't think he's got a chance. Maybe the first DLC.
He never was a grappler though, in his original incarnation he was quake/projectile user, and in fanmade games he employs earth element things like rocks and sand.
Rain- just no. If anything this should be Reptile, who's got a hell of a lot more plot relevance right now than Rain would. I'd like to see him, but I don't think this is likely going to be a thing.
My guess is that reptilian character will be a newcomer but possibly an offspring of Reptile/Khameleon.
He was a boss in MK4 and totally playable, and has been playable in almost every game he appears in. I'd bet on him being in the cast in some form or another.
His first appearance as boss was the "big unplayable-too-unbalanced-to-be-playable" type boss in MKM. I doubt anyone can take Shinnok's MK4 appearance even remotely seriously aside of maybe his Fatalities, so that's not too indicative of ways he should go as a character. As for MKA, that was just one big Trilogy with everyone and their mother being playable. By that logic, Shao Kahn was unplayable in MK2/MK3 series then playable in MKD,MKA and MKvsDC which means he was playable in more games than he was unplayable in - which means they should've made him playable in MK9... but they didn't.
If you sit down, and explain the plot of the original mk's to a layman, they'll look at you funny. It's, at best, fanservicy trash. MK9 took that, and managed to make it "mediocre comic book" levels of good, which is a significant improvement. The good stuff is kept, the bad stuff is just dropped, and the rest is ironed out and presented in a much more sane and well organized manner. I expect they plan to continue this trend.
MK's storyline is more of "wide" instead of "deep", that is they keep on adding new elements while leaving many of them without further development, and are taking inluences from various mythological things while keeping them not-too-deep. Prime example is just slapping a name of creature like "Oni" on few characters without going into actual Oni stuff from japanese mythology, or why Raiden and Fujin are seemingly working full-time in China as gods while having japanese names. It's like "that sounds cool, let's use it". They just put a big bunch of everything and expect it to somehow work together.
In MKA that led to far too many loose ends and unability to create biographies for most of characters, so in MK9 they were cutting corners, but MK9 storyline instead created a huge amount of plotholes when compared to previous one, and there were multiple threads pointing each one of these out (Shao Kahn's unability to conquer Earthrealm being due to Sindel's magic and not MK Tournament rules, Quan Chi wearing Shinnok's Amulet in plain sight and no one giving a fuck, infant Mileena and her lack of any kind of relationship with Kitana or Baraka, Shang Tsung playing no role in Sindel's resurrection and Sindel's subsequent braindead plotline, the list goes on). At least their "story twists" managed to surprise even Tobias, not in a good way.
but I really don't think introducing the realms of order and chaos are the likely routes here. I have been looking at the levels shown, and they don't seem to be places we've seen before, and one thing i've been thinking is that it's because it's earth after Shinnok's success, and the 25 years later is under his rule sort of thing(levels certainly don't look like order/chaos lands, but if that was a surprise they'd obviously be saving those so meh). If this is correct(blind theory I know) you really don't have room to start throwing in plotlines linked to other realms. Especially when we've got a bunch of new characters they need to introduce and start building up(and again, none of them scream order or chaos realm to me).
Initial conflict is versus Shinnok but that will be only beginning of game's storymode, who's not to say that plot will then become more global (the realms are at stake, etc)? MK Team couldn't leave out Order/Chaosrealm that much they even included them as Challenge Tower backgrounds in MK9 (and MK9 was not supposed to have any sort of relation to those realms), and they were also mentioned in Cage/Noob endings. To me it is clear that the "big six" realms thing is here to stay. Moreso, Order/Chaosrealm have no need of own plotlines, you just take any plotline based on other realm and Order/Chaosrealmers are attaching to it automatically after evaluating the sides of conflict in terms of order and chaos (just like in MKD). And as those realms have only handful of playable characters (not surprising considering their late introduction), newcomers from them are very likely to balance out the overall MK roster between various realms. In particular, there were many guesses about Ferra/Torr being possible Chaosrealmers (seeing how Mad Max universe works, it is somehow similar).
I would be SHOCKED if it revolves around Onaga, all the realms, and the Kamidogo, and isn't instead streamlined in some way to make things more coherent, and to mix it with the shinnok/quan attack and maybe the power void left by Khan, and the Edenian succession+whatever new stuff they bring.
Count in how many game storylines Kamidogus/Onaga appeared, and then compare it to number of Quan Chi/Shao Kahn/Edenia etc appearances. Continuing with slapping more Quan Chi and Edenian damsels in distress on us even in later parts of MKX story would be an overkill and epitome of redundancy. I honestly hope Quan Chi and Bo' Rai Cho collide with each other and self-destruct like 15 minutes after MKX story mode starts.
