We will have to see. The strength of the Xbox brand in the US is still very strong, especially with the 360 still dominating over there. That said, it's not impossible. Both MS and Sony played all their card tonight, and Sony certainly came out far ahead.
I agree that the Xbox brand is strong here in the US. But for the average consumer to choose between $499 or $399, that's a big difference
It'll depend on whether people think the +$100 is worth it for kinect, since Sony doesn't include their camera in the package. If it is compelling enough to the general public, it will do well like Wii. Sony will probably capture more of the "hardcore" gamers.