1. The roster will only have 30 characters, as confirmed by Ed Boon.
2. Ed Boon has clarified that there will be 14 brand new characters, 8 returning characters MK9, remaining from the older versions of the games.
3. Shao Kahn and Kotal Kahn are not related. According to sources, Kotal Kahn is related to Shinnok.
4. Liu Kang, Tanya, and Reptile are likely to be playable characters.
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Unfortunately, there's no good news source on this one. I found it on Tumblr, Googled it, and found it on Facebook. So it may not be true. But I figured, going off these rumors, it'd be cool to have a conversation since I know there are MK fans.
Talking about the 8 returning characters from MK9:
First off, I said "WHO? THEY KILLED OFF EVERYONE." But alright. We already know Scorpion & Sub-Zero, so that's two. That leaves six. My guesses: Raiden, Smoke, Reptile, Ermac, Liu Kang (ew), & Mileena.
As for the remaining eight characters from older MK games, but not in MK9: Shinnok, Fujin, Kai, Reiko, Tanya, Nitara, Bo' Rai Cho, & Frost.
Also, this picture of Ermac, is fanart, created by Bernard Beneteau who happens to be a senior artist at NetherRealm Studios.