Hopefully they fix it in iOS 11 since any device which won’t run 12 will be vaunerable. I’ll need to go back to any older iOS device I’m still using which won’t run iOS 11 or 12 and use the longest password allowed. That’s gonna be a real pain, as I currently use 4-digit passcodes for easy access without Touch ID. But it’s probably a good idea for any device even running iOS 12 since there’s a one-hour window in which someone could steal a phone and get lucky.
Any device running iOS 11 can run iOS 12. They announced this at WWDC. Rest easy. (less)