When iPhone OS went to version 3.0, the number of home screens increased to 11. All three of Apple's "Touch" devices support 11 pages of apps.
I believe that OS 4.0 will bring even more app storing capability, with the ability to easily sort and categorize apps. Though on iPad, I'm struggling to fill the screens so far. Right now I don't see my iPad filling up with crap like my iPhone does, but who knows.