I bet that it has something to do with the tablet. Ads and printed media go hand in hand and this thing is primarily a media device. If it really is "the most important thing" Steve has ever done it has to be much more than a big iPhone. I think the significance will distribution of media more so than the device itself. Look at the iPod and the iPhone. They're wonderful, but what really gives them staying power are the iTMS and the App Store. I'm betting the tablet won't be the big story after all.