While Chris Nolan and Co. may have known for certain who the primary villain in Dark Knight Rises was years ago, everyone else only found out at the beginning of 2011. Heck, even after Tom Hardy was officially confirmed to portray Bane in the film, rumors continued to circulate that someone like Dr. Hugo Strange (in some capacity) would also face off against the Caped Crusader in Nolan's trilogy finale!
There is one well-known Batman antagonist who has long been rumored to appear in the movie; however, to further discuss that subject - and, to address a recent story that seemingly confirms the character's involvement in Dark Knight Rises' plot - we'll have to venture into some potential spoiler territory. You've been warned...
POTENTIAL SPOILERS AHEAD!
The Batman villain (or, rather, villainess) in question is, of course, Talia al Ghul. Dark Knight Rises' starlet Marion Cotillard's evasive comments about her role in the film only heightened suspicions that she is secretly portraying the daughter of League of Shadows mastermind, Ra's al Ghul; amateur footage of the film's production also revealed Cotillard on set, dressed in a militaristic outfit and climbing into (Bane's?) camouflage Tumbler. As far as some fans are concerned, that's more than enough to suggest that Cotillard is indeed playing Talia.
Add one more piece of "evidence" to the pile, in the form of a Surry Comet article about eight-year-old Sutton actress Leilah De Meza being offered the part of "young Talia al Ghul" in Dark Knight Rises. According to her mother, Meza ended up taking a pass on that Dark Knight Rises role, seeing as the young girl would've had to shave her head for the part - something her parent felt "could have affected Leilah's confidence and general social welfare."
If we assume that at least a young Talia is slated to show up in The Dark Knight Rises, then she will almost certainly appear via the flashback scenes to a young Ra's al Ghul (Josh Pence). There's already rampant speculation going around that Joey King may be the underage actress who actually portrays the shaven-headed Talia in said sequences - some of which were hinted at in a now-defunct Dark Knight Rises prologue description.
That said: at this point, it would be more shocking to learn that Cotillard isn't portraying the adult Talia al Ghul - who has ties to both Bane and the League of Shadows. That's no guarantee that the character won't be featured solely as an adolescent in flashbacks (assuming she does show up, at all) but, still...
All shall be revealed when The Dark Knight Rises hits theaters around the U.S. on July 20th, 2012.