Valve has officially rolled out the first beta for Dota 2 Reborn. They go into extreme detail about some of the new features that are now possible in Dota 2 thanks to the advancements offered by Valve's own Source 2 game engine.
It's kind of strange that the Source 2 is being introduced through the free-to-play MOBA Dota 2, but that's just how Valve rolls.