Start over, about 5-7 years after Nolan's Batman 3, at least. Doesn't have to be another origin, but at least a completely separate storyline/history with a fresh canvas. They could do a different Harvey Dent if they want to, or another Joker, or as yet unused characters. But I'd like Nolan's trilogy to stand as its own unique take on Batman in both style and storyline. Batman doesn't have to be an ongoing movie series like Bond (which I feel was sullied, creatively, by having so many installments)...which had to start over themselves after running themselves into the ground. Let different creators have their own individual take on them for different generations and not be obligated to continue/adhere to any storylines from previous takes.
They should take a break for a while from Batman movies after the next/last Nolan ones. It'll be a fresher introduction, and better for them overall as films first and foremost. There will always be plenty of serial Batman in comics/TV/games/etc, but let the films be more rare as events. It helps them be richer when they're good, and less redundant when not so good. As good as these films are, I think it would be a greater honor to them to let them close out on their own terms and maintain their own unique place in their cinematic generation, than to keep trying to build off of it. Let future filmmakers do what they want with their storyline/style/etc, and give this one the space it deserves.