So from reading the CBPeripheralDelegate documentation, it appears that RSSI and peripheralDidUpdateRSSI:error: were deprecated with i
There is a known issue that has been posted about this on the Apple Developer forums to which I have an open radar as well.
The issue seems to be that the new callback method peripheral:didReadRSSI:error: is never called on iOS 8 specifically after the initial connection is made to a peripheral. The only resolution I have found is to reset bluetooth on your phone by turning it on/off or restarting the phone.
Here is the link to open radar I filed.
Just tested my example that was displaying this issue with the current 8.2 release and I am no longer seeing any issues with the new iOS 8 delegate method never being called. I am marking my radar as resolved per the 8.2 release.