That is all in the hands of the carrier of they decide to push the update. For example, in the USA, neither AT&T nor T-Mobile have mentioned their intentions to update the 925s that use their network. AT&T hasn't even pushed Lumia Denim for its version of the 925. Same goes for the 1520. If any phone should get the official update, it would that since it is a flagship device. You can technically update to the current RTM build via the insider program and bypass the carrier. It's almost a wait & see game right now.