SEGA bought Relic because Relic has the WH40k games license, which basically prints money. COH2 was just something that came along for the ride and if SEGA is pushing Relic to do something it's probably to work on DOW3/Space Marine 2.
As I understood it, Relic only owns the rights to the Dawn of war series of games (if that is not what you meant already). For any other game that is a Warhammer/40k game but not another DoW installment Relic would have to set up a new contract with GW
Not that I care. If I was Sega, I'd be very interested in a new DoW game. I think singleplayer wise those games are far more substantial than CoH..
Having said that, fuck me if I didn't enjoy the original CoH campaign immensely!