Oh god. If you're going to "wait for someone to hack the security" you're screwed. You have a better chance of getting a phone implanted in your brain than that happening. LOCKED BOOTLOADER. I don't know what else I can say on that. If the security on the device doesn't allow you to go back to a previous version, then you aren't. You will brick your device trying. The ONLY thing we can do is move between updates on the same security level. Please, please, please understand this fully before attempting to go forward. The ramifications of not understanding this are perilous.