Last night my iPod Touch iOS9.2 wifi totally stopped working.
The swipe-up control panel shows a dark grey circle instead of the wifi status, and tapping it does nothing.
The toggle switch in Settings / Wi-Fi is stuck off and greyed out, unresponsive.
After a full iOS reset/restore and restore from backup, and even with Reset All Settings, the problem remains.
At this point I have to recommend DO NOT UPGRADE to any version of iOS9 on any iOS device.
I’m investigating the feasibility of downgrading the iOS version. The last fast & reliable version of iOS that I remember was iOS 7.1.2.