Belgian magazine PCGameplay is reporting a sequel to Warhammer 40,000: Dawn of War is on the way, according to IGN.
Only two classes, Orkz and Space Marine, have been mentioned so far. There will be co-op campaigns for both. It's also being reported that the game will support DirectX 10 and multiple CPU cores.
Relic has been developing the game since September 2006, and it's due out next year.