According to Microsoft who released the statement to the folks at Windows Phone Central, it seems that there could be a firmware issue that gave Microsoft enough reason to halt the rollout of the update. “We have paused delivery of Windows Phone 8.1 Update to customers with the HTC 8X and HTC 8S who are using the Preview for Developers. Microsoft and HTC have identified an issue and are actively working to fix it, and will resume delivery of the update once a fix is in place.”
Some believe that the issue could be due to a bad driver, but either way it seems that in order for HTC 8X and HTC 8S owners to receive the update, they might need to update their firmware first before getting the Update 1. It is unclear as to how long Microsoft might take to fix the issue or for HTC to push out a firmware update, but hopefully it will be soon. We’ll keep our eye on the progress and will update you guys accordingly.