For licensed sets, Lego is typically given advanced knowledge (concept art, etc) of items before they are released, so as to be able to have sets designed, manufactured, and ready to sell before things (shows, games, etc.) go live. Depending in the IP and licensing agreements/contracts, this can (and has several times) resulted in the release of sets well before the things/characters/scenes they are depicting "come out."
So not really a prediction. If anything, Mojang probably told Lego it was going to be a thing, and Lego made the set, then Mojang pushed back their internal schedule and delayed actually adding it to the game, causing the set to be released well before the game update.
