Just like on iOS 7, users can update their iOS devices to iOS 8 without a registered UDID. To do this download the iOS 8 ipsw ( look for it, we’re not providing a link to it ), plug in your device, load iTunes and hold Option ( Shift ) and click on Update or Check for Update in iTunes. Select the iOS 8 ipsw that you’ve just downloaded and install. Mare sure you click on the update button and NOT the restore button in iTunes. Also, it’s probably a good idea to turn off Find my iPhone.
NOTE: if you update to iOS 8, you can kiss your jailbreak goodbye.