I think jail breaking will never come back. I'd bet that iOS 7 will never be jail broken.
They are close right now...it'll be back. The real question is, when will the jailbreak for the iPhone 5S be available (due to the processor)...THAT will be the biggest hurdle.
iOS 7 Jailbreak: First Look At Cydia Port For iPhone [Image Gallery] | Redmond Pie
It's kinda simple really...The developers of the jailbreak test the jailbreak on that device to make sure that the jailbreak works on the device before releasing it to the whole world. But the more updates Apple releases for iOS 7, the longer it will be until the jailbreak is actually out.