In minecraft, when will emerald ore be released on xbox 360?

Well going by this

http://minecraft.gamepedia.com/...g_features

it should be in TU14 which is the next update for 360. It says it's equivalent to pc update 1.3 which was when emerald was introduced in the pc version

http://minecraft.gamepedia.com/...on_history (scroll all the way down, you'll see pc update 1.3 and all its info)

though nothing has been said about the xbox 360 TU yet…

According to the source, there's no information on plans for the next Xbox update. Basically, we don't know.