A good news for DotA fans, John St. John (Known for the voice of Duke Nukem) confirmed he had some recording at Valve for DotA.A couple of days ago, John St. John said this via twitter

-Had a great time in Seattle last week recording for DotA. The guys at Valve Software are awesome! Going to PAX? Might see you there Sept3-5

Thus confirming that the game Valve hired DotA creator Icefrog to make with them, is indeed Defense of the Ancients.