The DayZ team has posted a new blog on the official site. The post starts with stating the obvious: The standalone version of DayZ that was originally scheduled to be released at the end of 2012, has not yet been released. Instead, a limited closed beta is scheduled to begin "imminently".
Put simply, DayZ Standalone isn’t here because we had the chance to go from making a game that was just the mod improved slightly, packaged simply, and sold - to actually redeveloping the engine and making the game the way we all dreamed it could be. This blew any initial plans we had dictated to pieces.
Read the entire blog on the DayZ site.