I would argue it already has reached appliance level familiarity. Do you know anyone between the ages of 7 to 60 that doesn't know how to use an iPhone (or iPod, or iPad) with ease? Probably not many.
But the UI feels stale after a while. I would argue that a significant UI refresh that peaks the interest of your users and excites them to upgrade is better than appliance level familiarity. If the familiarity is the measure of success then why do car companies constantly redesign their interiors, or why do appliances change their colors or button layouts from year to year?
Are they wise to do that? I recently replaced a broken microwave with as similar a model as I could find, from the same company. But I would have paid more to avoid continuously stubbing my fingers on their design regressions.
That is a good point. New is not always better but consumer products need to be "new and improved!" in order to give the customer a sense they are buying something better than the model from five years ago.
But at the same time I can't help but feel that progress can only be made with change and at this point Apple can't keep relying on minimal hardware advances to keep their marketshare.
> consumer products need to be "new and improved!" in order to give the customer a sense they are buying something better than the model from five years ago
Where is the proof of that? I feel that it's an "internet truth" where early adopters have the loudest voice. Yet Apple is full of cash earned on machines that look almost like their predecessors (iPad 1-4, iPhone 1-3GS & 4-5, similar for the Mac).
The refactors often rely on the fact that for every one of you (and me) there are 2x or more of new users who want something looking fresh and appealing, even if we see it as a regression (just don't go too far like MS did with Metro)
I don't know if it's possible, but if they're constantly making changes it certainly won't be.