Karen Strassman favorited a tweet from @shinnokfan and because of it, I'm 100% sure she will do the voice-over for Mileena.

Mileena=foot 4 of the boot hint.

You guys know that, despite having a voice actor, Mileena could easily be NPC, right?

People who aren't in a game CAN'T be legally prevented from talking about the fact that they're not in the game, BECAUSE THEY'RE NOT IN IT.
You have to be under a contract and have signed a non-disclosure agreement in order for legal to make you do anything.

Duh.
That's my whole point. ANY time an actor plays coy or says maybe, it means they're under contract, which means they ARE in the thing. If they weren't in it, they'd be able to say "Sorry no, haven't heard anything, they didn't ask me back for that one" or something similar, because they wouldn't want to mislead and disappoint their fans.

Sure, but she won't be a NPC.

She could always be voicing both Mileena and Kitana. It's entirely possible only one could be playable and the other could show up in story mode cutscenes.

IF she's in and not just fucking around with fans.

I think she'll be doing the voice for Kitana and Mileena. I think Mileena is the most likely of the two to be playable. But Kitana will be in the game somewhere.