Rumor has it that Apple is working on a new kernel-level security feature for iOS 9 and OS X 10.11 called Rootless. While this could be a huge blow for the jailbreaking community, this could have a widespread impact on other areas, such as law enforcement.
According to sources within Apple talking to 9to5Mac, the new Rootless feature will "prevent even administrative-level users from being able to access certain protected files on Apple devices," making the devices much harder to crack. The most obvious casualty of this will be the jailbreaking community, since they rely on such access to the underlying operating system.
But such a feature is also likely to affect law enforcement's ability to access iPhones and iPads, since some of the forensic tools used rely on vulnerabilities to be able to access locked smartphones.
Apple took steps in iOS 8 to make the operating system more robust against attack, but while it was a step in the right direction, it didn't offer complete protection. On top of that, the trusted pairing record that the iOS device created when backing up to a PC or Mac also left devices vulnerable.
The bottom line is that the more secure iOS is against jailbreakers, the more secure it is all round. Code doesn't care if you wear a black hat, grey hat, or a blue one.
But writing secure code is hard, and Apple has been trying to make iOS resistant to cracking for years without success. Every time Apple throws down the gauntlet, the jailbreak community rises to the challenge. On top of that, as pointed out iDownloadBlog, the last public jailbreak of iOS to use a root kernel exploit dates back to late 2013, so Rootless might not have that much of an effect on the jailbreaking community after all.