I really don't know what to expect of Halo Wars. It's a console RTS but it has both the Halo brand and not many big games (exclusive) released for Xbox at the same time, so who knows... Maybe half what a Halo FPS can sell...
I expect KZ2 to sell well but not crazy, at best it could have COD4 (PS3) numbers.
I'd say it will be a tie, but I wouldn't be surprised if I was totally wrong. It happens often.
They will know Helgan belongs to Helghasts