The latest version of iOS 6.1 is currently being beta tested as we speak, and the update will end up fixing that pesky lock screen vulnerability that's probably not as huge of a deal as people are making it, but nonetheless, it's there. However, iOS 6.1.3 also comes with a fix that finally blocks the infamous Evasi0n jailbreak.
The Evasi0n jailbreak has fought a good battle so far, surviving both iOS 6.1.1 and iOS 6.1.2, but Evasi0n team member David Wang (a.k.a. Planetbeing) has confirmed that iOS 6.1.3 will block some of the exploits used by the dev team to jailbreak iOS 6 devices. Wang says that his team doesn't yet have a fix for the update, and isn't sure if there will be one.
Then again, over seven million iOS devices, and counting, have already been jailbroken under iOS 6.0 and iOS 6.1, so most of the damage has already been done. The jailbreak patch-up in iOS 6.1.3 will mostly just mean that jailbreakers won't be able to update to this newest version, thus leaving their devices still vulnerable to the lock screen exploit.
Forbes notes that the reason why Apple is taking its time patching up this specific jailbreak is because it poses as a low security risk for Apple. Unlike JailbreakMe, which simply involved heading to a specific website in your mobile browser and hitting go, Evasi0n requires a bit more work that fewer iOS users are willing to try out.