Today, Valve announced the update, titled Three Spirits. And true to the Dota team's word, it's a big one. It includes two new heroes in the form of Earth Spirit and Ember Spirit (counterparts to the existing Storm Spirit), an in-game coaching mechanic that enables teams and individuals to improve their play, and a crafting and socketing system that provides for customizing existing items or combining unneeded ones to make something better and more useful.
The patch also brings a new showcase view of matches, a lane-picker, colorblind mode, new training missions and more. Oh, and yes, Diretide is coming; the event runs from November 14th to November 28th.
Check out the full patch notes on the official Three Spirits site.