You'll have to wait for a ROM.
There's a guy on XDA-Developers who posted an email from LG customer service stating that his Optimus G will not be receiving KitKat. It's a damn shame considering that its the cousin of the Nexus 4(which isn't receiving Kitkat just yet).
Nexus 4 - Stock 4.4.4 Sweet, delicious KitKat
Samsung Galaxy S Captivate - 4.4.4 via CM 11.