It's really hard to tell how The Conduit will do but I think once we figure out how CoD: WaW does we'll get a better idea. So far the only traditional shooter we have "complete" sales on for Wii is Red Steel and it went platinum. If I had to guess, though COD3 did about 600,000 and MOHH2 did about 500,000. So think if CoD: WaW is able to do over a million by the time The Conduit comes out then the The Conduit will see success. Anywhere from 1-2 million. But if CoD: WaW doesn't do that well then it's hard to think an unproven franchise could go anywhere despite the hype.
But as stated The Conduit has pretty damn good hype right now with most things being said about it pretty positive... aside from one reviewer knocking on it for being unoriginal but so are all shooters these days. As long as their is a base on Wii to buy the shooter then they'll show up on those first days and put it up high which will draw the mainstream in later.