It's impossible that the Graphics be like Halo 3, mostly due to the fact that many more units are being rendered at once. Unlike Halo 3, where you only fight 15 units (At most) at a time. In Halo Wars, you will be fighting FAR MORE then that. Plus, Graphics aren't important, Gameplay is. Look at Starcraft and World of Warcraft. The most popular games in the world right now and the graphics are outdated.
I know you are expecting some witty remark, something funny that is usually found in some signature. Well stop looking because you won't find one here.