Ever since Mirrodin Besieged, R&D has been designing two Event Decks for each set to serve as a "step up" from the Intro Packs. These decks have contained any number of Standard-legal sets among their cards, not just the sets that they are made for, and are tuned to be playable out-of-the-box at competitive events. There have been eighteen so far, as Monty Ashley's Magicthegathering.com Arcana article from today points out, and as of this spring there will be... nineteen.
That's right - as of Dragon's Maze there will be only one Event Deck per set created. The Arcana doesn't actually explain the reason for the move, why R&D chose to change policy with the last set of a block, or whether it's temporary or indefinite.
The Return to Ravnica and Gatecrash Event Decks were guild-focused, though they didn't revolve entirely around the Ravnican guilds since they had cards from Innistrad, Dark Ascension, Avacyn Restored, and Magic 2013 in addition. All five colors are represented already among the four decks. This points to a non-guild-based deck to be released for Dragon's Maze. It's distinctly possible that we'll see our first five-color (or omnicolored) event deck with the Dragon's Maze release, and most likely the guild logos of the previous two sets' Event Deck boxes will be replaced with card art, which was always used prior to Magic 2013.
What do you think of the change in Event Deck policy, and what do you think the Dragon's Maze Event Deck will look like? Let me know in the comments.