If you couldn't understand what Tom Hardy as Bane was saying in the trailer, you're not alone. Rest assured, Christopher Nolan says; “I think when people see the film, things will come into focus. Bane is very complex and very interesting and when people see the finished film people will be very entertained by him.”
Here's more from EW on the plot, which takes place eight years after "The Dark Knight" ends:
Fans may want to revisit that second film, as Nolan tells EW that the last chapter of his cinematic saga explores the ramifications of The Dark Knight’s chilling climax, in which Batman and super-cop Jim Gordon (Gary Oldman) hatch a conspiracy to cover up the sins of Gotham City’s so-called “white knight,” the late Harvey Dent, a.k.a. Two-Face (Aaron Eckhart).