LG is yet to release Android 4.3, yet alone Android 4.4 for Optimus G Pro. However, thanks to XDA, we have a clean AOKP ROM for it.
Installation instructions.
* Backup your data,reboot in recovery;
* Wipe data,cache and dalvik cache.(wipe system too for a clean install);
* Flash zip;
* Flash gapps;
* Reboot.
Download the ROM from here (Android 4.3). Android 4.4.can be downloaded from here. All ROMs are without Google apps, but can easily be added by downloading this package. Just flash it in recovery.