I don't think we're too far off a $299 80 gig system. Dell is actually a good example; they've been letting them out the door, albeit with coupon codes, for just a bit over $300, and they still can't move all their stock. With Blu Ray player prices dropping, and with TV prices continuing to drop (i.e., major electronics), there has been speculation we could see a $299 system this year.
Funny thing is, this was the year I was going to get one, but I just bought a dog and found out my wife is pregnant within days of each other. So it looks like I'm gonna have to make do with my 360 for a while.