So far there is only one source for this rumor (Bleeding Cool), and they have very little information about it. But I'm going to relay the info to you anyway, because I like rumors, and because, if true, this one would be awesome.
Are you ready? Cause here it is: David S. Goyer, the man who scripted the Dark Knight Trilogy and Man of Steel, is currently working on a Superman prequel television series called Krypton.
That's all we know right now. Perhaps it would focus on the relationship between Zod and Jor-El. Maybe it would be a courtroom procedural about a Kryptonian patent lawyer. Anything is possible—except the presence of Kal-el, because he wasn't born yet. Which means this show—er, rumor—would probably not exist without the success of that other DC Comics superhero prequel show, Gotham.
This is all be good news if you liked Man of Steel and its Krypton scenes. (Which I did.) And seeing as how Bleeding Cool has been right about other big stories in recent months, we need to give this rumor some credence.