Android 4.5 ( Android L ? )

Android 4.5 (Android L?) is not yet released. Google has not yet announced the release date. If you are a developer, you can take a look at Android L Developer Preview. Once the official Android L is released, your OEM (LG) may think of porting it to your phone model (LG Optimus G Pro), and after the porting is completed and tested, LG may provide the OTA update.