If she doesn't turn out to be Talia, then f*** this movie.
But thankfully, all signs point to it being so:
A young Ra's in flashback is CONFIRMED
Which means League Of Shadows appearance is CONFIRMED
Bane, her sometime lover is CONFIRMED
Heavy connections to Batman Begins are CONFIRMED
The League Of Shadows know Bruce Wayne is Batman CONFIRMED in Batman Begins
And then there's the leaked plot outline about Bane & Talia vs. Batman & Catwoman which some vaguely seemed to verify (LR, BOF etc.)
So: Miranda Tate, Bruce Wayne's confidante and lover, will reveal herself to be the daughter of Ra's Al Ghul and the new head of the League Of Shadows at the end of the second act, with Catwoman coming to Batman's aid in the third. Simple.