It seems like Nolan's follow up to the Batman trilogy is the sci-fi film involving wormholes and alternate dimensions, Interstellar. The script was written by his brother, Johnathan Nolan, but not much more is known about the project other than the story being based on the theories of Kip Thorne (a theoretical physicist at Caltech).
Interestingly enough, Steven Spielberg was once attached to direct this feature, but had to back out for some reason. It's most likely for the same reasons that attributed him putting the kibosh on the robot apocalypse. Look forward to more information in the next couple of months.