A pre-release version of update 1.4 for Minecraft on PC has just been freed up for download. It has been referred to in the past as the “Pretty Scary Update”, where a new boss is introduced - in the form of the Wither.
As well as him, there will be new mobs and improved commands amongst other things. Most of the insights will be to do with technical phenomena. It is in the anticipation for the release of the full update on October 24th.
The official site has it up, even though the update was to “prepare server admins and mod makers”. It should prove a worthy trial.