Q&A Session #4 on the DotA Forums has answers from IceFrog, developer of the Defense of the Ancients modification who was hired by Valve last October. One of his replies to community questions indicates we may not have to wait very long to see what he is working on at Valve: "It certainly won't take that long. There are a lot of very talented people here at Valve that are working hard on it every day to ensure high quality in a timely manner. We'll be making an announcement soon actually, and based on the feedback I've been getting since the last mention, I'm sure you all will be as excited as I am." Thanks Rock, Paper, Shotgun.