In my opinion, Tanya should have been on the Mortal Kombat X roster right from the start. It makes no sense to me why she is featured in the story mode and then gets relegated to paid DLC while characters like Jax, who shows up for one chapter and then disappear for the rest of the story get the main roster treatment. Even some of the new characters like Erron Black and Ferra/Torr spend all of 5 seconds in story mode and then never show up again.
Anyways, Ed Boon confirmed that the MK4 original is coming next week.
If you are a Kombat Pass holder, you will get Tanya on June 2nd. Non Kombat Pass players will get her a week later on the 9th.
No other details have been released at this time although she will most likely come with a skin pack, and if I had to guess, I would think that it would be one of the Klassic skin packs since Tanya is technically a Klassic character.
No word yet on what her variations will be but I am hoping that NetherRealm will hold a stream this Monday to show her off like they did when Jason was released.