If you have not downgraded from iOS 8.4.1 to iOS 8.4 for the time being since you have upgraded to iOS 8.4.1 to fixes the bugs in Apple Music to enjoy Jailbreaking again, then it is quite unfortunate that you can long longer downgrade from iOS 8.4.1 to iOS 8.4.
Conventionally, Apple do keep previous iOS update for few number of days for iOS user who might want to downgrade from their recent iOS to the previous one but after some time, the door would be short totally and there would be no way to downgrade from recent iOS to the previous iOS.
Apple has stop signing iOS 8.4, their by making it impossible to downgrade or upgrade your iOS without losing your jailbreak. If by virtue of willingness or grace, you updated your device via iTunes, you will automatically be upgraded to iOS 8.4.1, and now, you can no longer select your firmware as iOS manually again as iTunes will not recognize it as the current firmware, rather, it will only recognized iOS 8.4.1
If you want to stay jailbreak your device, you must maintain iOS 8.4. It is advisable to be cautious of the kind of tweak you install from Cydia this day, most especially those tweaks that are new. Also, do away from most beta release you don’t trust and go with tweaks from repo and that you are actually safe with them as this is the only way to stay ahead of being restoring your device in case things went wrong.
As at now, no one can predict exactly when the next jailbreak will be released but hopefully, it’s going to be soonest with iOS 9 around the corner
By Mid September, iOS 9 should be released, and with the iOS beta out there, there is a tendency to have a loop hole that would enabled us jailbreak again on the new firmware.