How much off should I expect for "last year's" model?

I'm looking to buy either a Mazda3 5-door or a Subaru Impreza 2.5i Wagon in the next week or so. With the 2008 models coming out now, is there a standard or expected percentage off the sticker-price or MSRP that I should expect off the 2007 models?

I know there are usually factory-to-dealer incentives for many 2007 models, but its hard to know how much these are. Does anybody know details about what I should expect if I purchase one of these cars?

Thanks.