Dota 2 Reborn has just been unveiled. It's a major update for the game, and it'll mean a shift over to a new engine (Source 2 anyone?), and it will feature a new interface and support custom matches. Here's what Valve has to say about it:
Today we are announcing the Dota 2 Reborn Beta, which brings with it a new interface, new engine and Custom Games. Everything in the dashboard has been completely redesigned utilizing a new UI framework, and the engine that powers the game has been fully replaced. On today's update page we will be giving you a preview of the new interface. Early next week we'll be talking about Custom Games, and later that week we'll conclude with various details about the new engine and launch the open beta.
Throughout the beta we'll be releasing frequent updates in order to fix bugs and make changes based on the feedback you provide. As you browse around in the new client, you'll notice a few things that aren't fully functional yet. Additionally, our focus has been on the dashboard so you'll find the in-game HUD currently looks the same.
There's plenty more information regarding the update over on the Dota 2 website, so head there if you want to get all the details.