I wonder...
It's conceivable to me that we might see a schedule next year very much like the one this year: iPad in the spring, iPhone in summer, iPods in fall. Software updates sprinkled around to keep the story fresh for each product line.
Desktop computers? Laptops? Who cares?
In one of Steve's recent guerrilla emails, he said that there will be a major Final Cut Studio release by the end of the year, but that has nothing to do with the holidays. My guess is that if the release was ready, they'd have shown it at the National Association of Broadcasters convention in April, which is where they've rolled that stuff out before.
The one part of the calendar that we KNOW is that there won't be any major January releases coming out of MacWorld. Maybe some new Nanos. But it's looking to me that releases will spread across the year, keeping something major in every quarter EXCEPT for Q4. That one will take care of itself.
In general, though, there's little history of major hardware refreshes less than a year apart.
And frankly, if you want to wait for anything, you might wait for this generation's price to drop waaaay down in anticipation of the new one...but seriously, buy the iPad now, enjoy the new software update late summer/early fall.