While we haven't heard much on the Android 4.3 update news front for the One or Galaxy S4 GPE other than "soon," it sounds like soon really may mean soon. HTC just released the Android 4.3-based kernel source and framework files for the One GPE on HTCdev.
The corresponding software version for the source and framework is 3.06.1700.10, while the kernel version remains unchanged at 3.4.10. You can download the kernel right here, and the framework files here. The Android 4.3 update that goes along with it will presumably be coming shortly. We hope.