Don't forget the marketing monster that Halo 3 is. I find it very likely that the 360 will outsell the Wii for one month, but after that I don't think so.
I agree that Halo 3 sales will be ridiculous. And I do think the 360 will outsell the Wii in the US in October. I just don't think it will outsell the Wii WW in October or any other month.