I'm not buying this trophies/achievements list. It seems too lazy and simple for NRS to do so. Around 20 trophies just for performing fatalities with a certain character? This could be a pretty big trolling after all. You just need to compare some difficult trophies in MK9 and MKX to the leaked ones. Hell, I didn't manage to have all of the MK9 trophies because of this ridiculous "Gain mastery of all fighters". I do have 100% in MKX but some of them were not that easy.
The other thing is the lack of male ninjas. I can't imagine NRS not to know about their popularity and the critics after releasing MK3. I don't think they'd dare to have the regular roster with only Scorpion and SZ being in. Scorpion and SZ are given, but Reptile is the third. He usually doesn't sit out. Then there are Noob Saibot and Smoke that were not in MKX. Rain being NPC pissed many people off. The only male ninja I can imagine to sit completely out is Ermac given that there are some endings with his souls being absorbed by Shang Tsung himself.
And if the trophies are indeed true, than there will be more spots on the roster. Similar to the stage select screen. Hence the diamond form of it. It may become bigger on each side without changing the form and is something new to a MK game.
It's something that every developer usually does on Steam (revealing trophy info).
The same thing happened with Dishonored 2, and it's how people found out that there was going to be a Standalone / DLC coming out for it before the trailer even came out for it.
You can monitor the activity for the game under the "packages" section and it shows when there was activity for the game being done on Steam.
It's unfortunate for them that it got discovered this way, but listing achievements / Trophies is something that devs will have to do before the game comes out, regardless.
NRS just happened to use the first 3 letters of their characters for their achievements, and people put 2 and 2 together and figured it out.
Again, I could very well see Reptile being 1 of the "unlockable" characters, as a nod to MK1, and the same goes for Noob and Smoke being possible MKII nod types of unlocks.
As soon as the leaks were discovered, the Steam db stopped updating, so who knows?
Perhaps those few other characters would have also been discovered.
While there could be a few more undiscovered spots for unlockable characters, I really don't think it'll be bigger than 25 for the default roster. IMO, it'll probably be 25 + Shao Kahn and the "?" box, in the same way that MKX was 24 + Goro and the "?" box.