Cameron said there will be extra 10 minutes, however with such a strong theatre numbers, I doubt the movie will be out of cinemas in less than 5 months. Then Cameron said give it at least 6 more months for the to "prepare" a Disc with all additional stuff. Cameron said first most likely you will see BlueRay which is more expensive (to the customer) then couple months later DVD. If the numbers at the theatress wont keep up, you will see DVD/BR disc in shops in upcoming summer.
ps. this movie, however, is definately worth seeing in theatres... I suggest watch 3D and IMAX versions both.