Business Insiders (Silicon Alley Insider's) chart using yesterday's Apple revenue numbers shows the iPad having an immediate impact on Apple's product matrix:
In the June quarter, the iPad business generated $2.2 billion of revenue for Apple.
That's more than Apple's iPod business generated last quarter... $1.5 billion. The price is a lot less per iPod vs iPad, thus units are still much higher. And it's almost half as big as Apple's 26-year-old Mac business, which put in its best quarter ever at $4.4 billion.