This game has been in development for the Wii for quite a while now, since early-mid 2008 at least and dev kits for Natal & Swand probably went out to developers back in maybe June or so. I'd rather they focus on making the best Wii game they can utilizing the wii for all it's worth, than worry about splitting attention to go back and figure out different motion controls and create HD assets which would only lower the quality all around at this point if they still want to make deadline.
Besides, I'm perfectly content with the graphical capabilities of Wii, but I also don't have a PS360 to compare it against, so it's kinda like I don't know what I'm missing, but that's fine with me.