Re: iOS 7 jailbreak yet
iOS 7 is a beta. Betas are small releases prior to the product being finished to give a larger group of people a chance to find bugs, intentionally or otherwise.
As bug reports come in, the build gets fixed and updated. The EASIEST time for Apple to throw together a quick patch to an exploit is while a smaller group of people have the iOS and they were intending to release another updated beta version.
So let's try an exercise in logic. If you find an exploit that jailbreaks iOS 7, do you release it now when it will benefit a very small group of people and ensure the exploit will not exist in the final, publicly released iOS 7... or do you hold onto it and hope Apple doesn't come across the same issue prior to the release?
When you figure that out, you'll realize how relevant their starting on a jailbreak isn't to a beta release.