Tell that to the automotive industry. How many cars do you think they'd sell if they looked exactly the same year after year and you couldn't tell a 3 year old model from a brand new one.Why must there be a redesign? There only so many ways to build a minimalistic touchscreen phone or anything minimalistic for that matter. Look at the iPod classic, Mac Pro, or iMacs since '08 etc...all those items have major design changes but recent year changes are minor ones.
I'm not saying Apple shouldn't try to innovate but at some point the design changes will only be "it's thinner & lighter than the previous version".
Change for change's sake is stupid. Change should happen when it's necessary.
And excuse me for disagreeing about the iPhone 4's design, but I think there's plenty of places to go other than the sardine can look.