I think the price drop was ready and they had the date set till after that games conference in case they had to make more drastic changes.
I think stock of the Pro is probably what makes them confident in their pricing. At $250, the 60gig pro is great deal. I don't think they should have removed the HD cable from the elite bundle, but for whatever reason they're confident about that.
As for Europe, I think the arcade bump might not be a big problem. People keep forgetting the Pro unit is still on the market. They probably have a bigger margin on the Pro and pushing the price of the arcade up, and dropping the price on the Pro will just encourage people to spend that little bit of extra money. Either way, both units are still cheaper than the PS3.
I think MS should be fine over the holidays. If Sony closes the gap, I don't think it'll be by a large margin. NPD should be a little interesting again.