Popular website 'Blu-ray.com' are reporting that 'The Dark Knight Rises' will be released on DVD/Blu-Ray on December 7th 2012.
Although this date could prove yet to be nothing more than a rumour, it would make sense given the time period from the film's release date and the likelihood of Warner Bros. making some serious cash over the Christmas period.
As for the artwork, yet to be confirmed, showing solely Batman, this will most likely be the final artwork, with both Batman Begins' and The Dark Knight's DVD/Blu-Ray covers showing only Batman, without any other characters from the films.