Responding to a question via Twitter, the official HTC account did mention that users are able to “expect the Windows 8.1 update to roll out to Verizon’s HTC 8X in late October,” although there is no concrete mention of an exact release date just yet. Apart from that, there was no estimates whatsoever from HTC on when the other mobile carriers, AT&T, T-Mobile and others, will be on the receiving end of such an update.
Taking into consideration how smartphones these days tend to arrive with such an update preinstalled, chances are all the devices and carriers will eventually receive the upgrade some time later in October. It would also be a watershed moment, since this update will, in all probability, be one of the last significant releases for Windows Phone prior to Microsoft making their collection of mobile devices make the move over to a new version of Windows.