I did a basic math count here, and, counting only the reebot games (MK9, MKX and now MK11), we get only 10 characters, that made it so far, the 3 games:
The 7 originals from MK1 : Johnny Cage, Liu Kang, Kano, Raiden, Sonya, Sub-Zero and Scorpion
Plus 3 from MK2: Jax, Kung Lao and Kitana
Outside these, all the other, only appeared one time until now, or twice.
Some of them that were in MKX, are being present again in MK11: Ex: Cassie, Jacqui, Kotal, etc
Some, that were in the previous 2 games, as Kenshi, Reptile, etc, will be absent in MK11
And you have these cases, as Sindel and Nightwolf , that only appear as playable in MK9, and as NPC in MKX, so, yeah, I think that now, they really have a good chance to appear as playable again in MK11
See Kabal ? He is playable in MK9, NPC in MKX, and returns now as playable again in MK11, so, there is something planned that NRS is following up, in order to pick who gonna make it in DLC option choice, hummmm .....