It will secure from the security issue that can be exploited in potentially various ways (jailbreak just being one of them).
Typically something like a security patch, especially one of higher importance that needs to get out sooner than later, won't get a dev/public beta.
The security changes are available from Apple, but they get listed within about a day or so after the update is released to give more people a chance to install the update and have the security issues patched before the details of those security issues are made public (and could potentially be exploited by someone on those who didn't get a chance to update). In this case it seems to have happened even faster:
https://support.apple.com/en-us/HT207026
Well, we even had an X.4 release (with iOS 8.4).
It's possible that with a security issue in play Apple might stop signing the previous version earlier than they typically do.
Why do you jail break?!
To address a security issue (that the jailbreak happens to use as well).
So...not actually bricked?
Tethering is generally in the realm of carriers and their plans/features, so it's not really something for Apple to allow.
[doublepost=1470336618][/doublepost]
It's not necessarily about it actually getting exploited as much as it being in existence and in the wild so to say. If it's there and it's known and someone could abuse it (even if no one really does) it's on Apple to address it. We all know that should one day someone actually exploit something before Apple patches it, everyone will be all over Apple for it, no matter how rare (even if just plain never) it happened in the past.