Mac laptops come in 11", 13", 15", [and 17"] sizes.
iPads now come in 7.9" and 9.7" sizes. You can argue that iPod touch is the iPad nano at 4" (they run the same O/S).
The 9.7" iPad doesn't seem outdated by virtue of screen size. But it feels awkward by virtue of thickness and weight.
So I think the next-gen full size iPad will be under pressure to slim down.