I know a lot of people with iPhones, and the older ones -- 40s and above -- don't seem so keen on the latest anything. They can all afford upgrades, but I see a good number carrying iPhones from a generation or two ago. The younger people (20-somethings I know) seem keenest on the latest devices.
My iPad 1 and 2 still work well, and Apple didn't tempt me with the latest iPad. I'd like get excited about a new iPad, but part of Apple's problem is they've already made me content. And stuff I'd get excited about, like SD card access, isn't something Apple offers.
I also know a good number of people with iPads (more middle age than younger ones) and they seem happy enough without upgrading.